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	$162.27	3.288%	$167.6054	$167.61	$167.60	$167.60
Purchase #2	$237.37	7.833%	$255.9632	$255.96	$255.95	$256.00
Purchase #3	$135.96	3.774%	$141.0911	$141.09	$141.10	$141.10
Purchase #4	$59.78	6.863%	$63.8827	$63.88	$63.90	$63.90
Purchase #5	$244.99	10.641%	$271.0594	$271.06	$271.05	$271.10
Purchase #6	$129.34	12.516%	$145.5282	$145.53	$145.55	$145.50
Purchase #7	$83.28	13.483%	$94.5086	$94.51	$94.50	$94.50
7 purchase totals =	$1,052.99		$1,139.6386	$1,139.64	$1,139.65	$1,139.70