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	$153.75	10.399%	$169.7385	$169.74	$169.75	$169.70
Purchase #2	$91.33	13.202%	$103.3874	$103.39	$103.40	$103.40
Purchase #3	$173.48	9.836%	$190.5435	$190.54	$190.55	$190.50
Purchase #4	$204.63	10.110%	$225.3181	$225.32	$225.30	$225.30
Purchase #5	$137.59	8.340%	$149.065	$149.07	$149.05	$149.10
Purchase #6	$237.87	13.401%	$269.747	$269.75	$269.75	$269.70
Purchase #7	$85.95	3.385%	$88.8594	$88.86	$88.85	$88.90
7 purchase totals =	$1,084.60		$1,196.6589	$1,196.67	$1,196.65	$1,196.60