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	$145.70	7.516%	$156.6508	$156.65	$156.65	$156.70
Purchase #2	$68.34	4.326%	$71.2964	$71.30	$71.30	$71.30
Purchase #3	$84.53	13.393%	$95.8511	$95.85	$95.85	$95.90
Purchase #4	$78.52	6.329%	$83.4895	$83.49	$83.50	$83.50
Purchase #5	$178.43	10.621%	$197.3811	$197.38	$197.40	$197.40
Purchase #6	$200.31	11.252%	$222.8489	$222.85	$222.85	$222.80
Purchase #7	$128.91	11.103%	$143.2229	$143.22	$143.20	$143.20
7 purchase totals =	$884.74		$970.7407	$970.74	$970.75	$970.80