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	$175.67	5.537%	$185.3968	$185.40	$185.40	$185.40
Purchase #2	$173.89	9.374%	$190.1904	$190.19	$190.20	$190.20
Purchase #3	$120.40	8.142%	$130.203	$130.20	$130.20	$130.20
Purchase #4	$240.49	6.209%	$255.422	$255.42	$255.40	$255.40
Purchase #5	$65.62	8.644%	$71.2922	$71.29	$71.30	$71.30
Purchase #6	$135.96	12.425%	$152.853	$152.85	$152.85	$152.90
Purchase #7	$84.44	13.420%	$95.7718	$95.77	$95.75	$95.80
7 purchase totals =	$996.47		$1,081.1292	$1,081.12	$1,081.10	$1,081.20