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	$24.57	3.846%	$25.515	$25.52	$25.50	$25.50
Purchase #2	$222.51	3.365%	$229.9975	$230.00	$230.00	$230.00
Purchase #3	$40.51	11.203%	$45.0483	$45.05	$45.05	$45.00
Purchase #4	$9.55	9.593%	$10.4661	$10.47	$10.45	$10.50
Purchase #5	$39.34	6.773%	$42.0045	$42.00	$42.00	$42.00
Purchase #6	$143.29	5.715%	$151.479	$151.48	$151.50	$151.50
Purchase #7	$207.96	11.238%	$231.3305	$231.33	$231.35	$231.30
7 purchase totals =	$687.73		$735.8409	$735.85	$735.85	$735.80