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	$186.77	13.597%	$212.1651	$212.17	$212.15	$212.20
Purchase #2	$58.71	12.153%	$65.845	$65.85	$65.85	$65.80
Purchase #3	$10.89	9.619%	$11.9375	$11.94	$11.95	$11.90
Purchase #4	$53.53	11.312%	$59.5853	$59.59	$59.60	$59.60
Purchase #5	$25.55	3.496%	$26.4432	$26.44	$26.45	$26.40
Purchase #6	$30.50	11.111%	$33.8889	$33.89	$33.90	$33.90
Purchase #7	$33.71	11.414%	$37.5577	$37.56	$37.55	$37.60
7 purchase totals =	$399.66		$447.4227	$447.44	$447.45	$447.40