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	$144.78	12.235%	$162.4938	$162.49	$162.50	$162.50
Purchase #2	$37.69	5.385%	$39.7196	$39.72	$39.70	$39.70
Purchase #3	$140.78	7.287%	$151.0386	$151.04	$151.05	$151.00
Purchase #4	$181.54	3.859%	$188.5456	$188.55	$188.55	$188.50
Purchase #5	$226.73	10.757%	$251.1193	$251.12	$251.10	$251.10
Purchase #6	$159.51	6.759%	$170.2913	$170.29	$170.30	$170.30
Purchase #7	$65.48	9.572%	$71.7477	$71.75	$71.75	$71.70
7 purchase totals =	$956.51		$1,034.9559	$1,034.96	$1,034.95	$1,034.80