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	$217.77	7.418%	$233.9242	$233.92	$233.90	$233.90
Purchase #2	$113.63	5.810%	$120.2319	$120.23	$120.25	$120.20
Purchase #3	$136.41	7.344%	$146.428	$146.43	$146.45	$146.40
Purchase #4	$173.98	11.738%	$194.4018	$194.40	$194.40	$194.40
Purchase #5	$15.84	5.819%	$16.7617	$16.76	$16.75	$16.80
Purchase #6	$59.41	3.449%	$61.4591	$61.46	$61.45	$61.50
Purchase #7	$116.33	12.806%	$131.2272	$131.23	$131.25	$131.20
7 purchase totals =	$833.37		$904.4339	$904.43	$904.45	$904.40