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	$10.82	10.454%	$11.9511	$11.95	$11.95	$12.00
Purchase #2	$165.33	3.256%	$170.7131	$170.71	$170.70	$170.70
Purchase #3	$62.86	13.306%	$71.2242	$71.22	$71.20	$71.20
Purchase #4	$168.83	9.682%	$185.1761	$185.18	$185.20	$185.20
Purchase #5	$31.72	3.779%	$32.9187	$32.92	$32.90	$32.90
Purchase #6	$153.52	8.723%	$166.9115	$166.91	$166.90	$166.90
Purchase #7	$143.29	9.446%	$156.8252	$156.83	$156.85	$156.80
7 purchase totals =	$736.37		$795.7199	$795.72	$795.70	$795.70