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	$146.63	3.288%	$151.4512	$151.45	$151.45	$151.50
Purchase #2	$139.49	7.666%	$150.1833	$150.18	$150.20	$150.20
Purchase #3	$96.48	9.352%	$105.5028	$105.50	$105.50	$105.50
Purchase #4	$222.72	13.697%	$253.226	$253.23	$253.25	$253.20
Purchase #5	$181.92	11.873%	$203.5194	$203.52	$203.50	$203.50
Purchase #6	$158.54	7.476%	$170.3925	$170.39	$170.40	$170.40
Purchase #7	$58.88	5.792%	$62.2903	$62.29	$62.30	$62.30
7 purchase totals =	$1,004.66		$1,096.5655	$1,096.56	$1,096.60	$1,096.60