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	$58.38	3.328%	$60.3229	$60.32	$60.30	$60.30
Purchase #2	$105.41	13.111%	$119.2303	$119.23	$119.25	$119.20
Purchase #3	$29.31	11.838%	$32.7797	$32.78	$32.80	$32.80
Purchase #4	$194.89	6.798%	$208.1386	$208.14	$208.15	$208.10
Purchase #5	$59.38	4.599%	$62.1109	$62.11	$62.10	$62.10
Purchase #6	$8.86	12.104%	$9.9324	$9.93	$9.95	$9.90
Purchase #7	$9.39	10.213%	$10.349	$10.35	$10.35	$10.30
7 purchase totals =	$465.62		$502.8638	$502.86	$502.90	$502.70