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	$247.61	3.131%	$255.3627	$255.36	$255.35	$255.40
Purchase #2	$105.47	5.793%	$111.5799	$111.58	$111.60	$111.60
Purchase #3	$60.71	6.759%	$64.8134	$64.81	$64.80	$64.80
Purchase #4	$136.89	5.202%	$144.011	$144.01	$144.00	$144.00
Purchase #5	$71.31	8.389%	$77.2922	$77.29	$77.30	$77.30
Purchase #6	$69.68	11.499%	$77.6925	$77.69	$77.70	$77.70
Purchase #7	$249.62	11.115%	$277.3653	$277.37	$277.35	$277.40
7 purchase totals =	$941.29		$1,008.1170	$1,008.11	$1,008.10	$1,008.20