Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$72.27	8.192%	$78.1904	$78.19	$78.20	$78.20
Purchase #2	$112.47	9.465%	$123.1153	$123.12	$123.10	$123.10
Purchase #3	$224.53	12.759%	$253.1778	$253.18	$253.20	$253.20
Purchase #4	$129.87	3.512%	$134.431	$134.43	$134.45	$134.40
Purchase #5	$105.96	5.375%	$111.6554	$111.66	$111.65	$111.70
Purchase #6	$188.43	10.488%	$208.1925	$208.19	$208.20	$208.20
Purchase #7	$145.48	6.447%	$154.8591	$154.86	$154.85	$154.90
7 purchase totals =	$979.01		$1,063.6215	$1,063.63	$1,063.65	$1,063.70