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	$156.54	3.324%	$161.7434	$161.74	$161.75	$161.70
Purchase #2	$41.47	13.229%	$46.9561	$46.96	$46.95	$47.00
Purchase #3	$50.43	5.405%	$53.1557	$53.16	$53.15	$53.20
Purchase #4	$184.73	13.540%	$209.7424	$209.74	$209.75	$209.70
Purchase #5	$40.32	5.559%	$42.5614	$42.56	$42.55	$42.60
Purchase #6	$244.73	4.790%	$256.4526	$256.45	$256.45	$256.50
Purchase #7	$175.72	11.624%	$196.1457	$196.15	$196.15	$196.10
7 purchase totals =	$893.94		$966.7573	$966.76	$966.75	$966.80