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	$185.76	3.845%	$192.9025	$192.90	$192.90	$192.90
Purchase #2	$183.58	3.733%	$190.433	$190.43	$190.45	$190.40
Purchase #3	$222.59	10.426%	$245.7972	$245.80	$245.80	$245.80
Purchase #4	$122.73	5.734%	$129.7673	$129.77	$129.75	$129.80
Purchase #5	$28.81	12.275%	$32.3464	$32.35	$32.35	$32.30
Purchase #6	$140.92	5.532%	$148.7157	$148.72	$148.70	$148.70
Purchase #7	$184.48	6.578%	$196.6151	$196.62	$196.60	$196.60
7 purchase totals =	$1,068.87		$1,136.5772	$1,136.59	$1,136.55	$1,136.50