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	$151.51	6.606%	$161.5188	$161.52	$161.50	$161.50
Purchase #2	$175.34	11.812%	$196.0512	$196.05	$196.05	$196.10
Purchase #3	$55.54	6.544%	$59.1745	$59.17	$59.15	$59.20
Purchase #4	$69.73	6.657%	$74.3719	$74.37	$74.35	$74.40
Purchase #5	$35.85	3.547%	$37.1216	$37.12	$37.10	$37.10
Purchase #6	$188.67	4.663%	$197.4677	$197.47	$197.45	$197.50
Purchase #7	$124.34	10.764%	$137.724	$137.72	$137.70	$137.70
7 purchase totals =	$800.98		$863.4297	$863.42	$863.30	$863.50