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	$52.67	13.223%	$59.6346	$59.63	$59.65	$59.60
Purchase #2	$17.42	4.547%	$18.2121	$18.21	$18.20	$18.20
Purchase #3	$95.58	5.158%	$100.51	$100.51	$100.50	$100.50
Purchase #4	$40.26	5.388%	$42.4292	$42.43	$42.45	$42.40
Purchase #5	$6.76	7.742%	$7.2834	$7.28	$7.30	$7.30
Purchase #6	$12.62	8.441%	$13.6853	$13.69	$13.70	$13.70
Purchase #7	$124.56	5.149%	$130.9736	$130.97	$130.95	$131.00
7 purchase totals =	$349.87		$372.7282	$372.72	$372.75	$372.70