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	$98.47	7.346%	$105.7036	$105.70	$105.70	$105.70
Purchase #2	$103.41	8.344%	$112.0385	$112.04	$112.05	$112.00
Purchase #3	$185.65	12.430%	$208.7263	$208.73	$208.75	$208.70
Purchase #4	$64.48	12.181%	$72.3343	$72.33	$72.35	$72.30
Purchase #5	$181.58	9.283%	$198.4361	$198.44	$198.45	$198.40
Purchase #6	$82.71	9.159%	$90.2854	$90.29	$90.30	$90.30
Purchase #7	$178.40	5.451%	$188.1246	$188.12	$188.10	$188.10
7 purchase totals =	$894.70		$975.6488	$975.65	$975.70	$975.50