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	$238.29	11.174%	$264.9165	$264.92	$264.90	$264.90
Purchase #2	$224.93	3.167%	$232.0535	$232.05	$232.05	$232.10
Purchase #3	$80.69	10.386%	$89.0705	$89.07	$89.05	$89.10
Purchase #4	$185.51	6.443%	$197.4624	$197.46	$197.45	$197.50
Purchase #5	$40.34	7.819%	$43.4942	$43.49	$43.50	$43.50
Purchase #6	$35.29	11.806%	$39.4563	$39.46	$39.45	$39.50
Purchase #7	$67.86	13.832%	$77.2464	$77.25	$77.25	$77.20
7 purchase totals =	$872.91		$943.6998	$943.70	$943.65	$943.80