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	$92.65	11.468%	$103.2751	$103.28	$103.30	$103.30
Purchase #2	$48.80	4.388%	$50.9413	$50.94	$50.95	$50.90
Purchase #3	$238.70	8.313%	$258.5431	$258.54	$258.55	$258.50
Purchase #4	$226.71	5.341%	$238.8186	$238.82	$238.80	$238.80
Purchase #5	$199.57	13.810%	$227.1306	$227.13	$227.15	$227.10
Purchase #6	$73.82	9.313%	$80.6949	$80.69	$80.70	$80.70
Purchase #7	$58.44	6.434%	$62.2	$62.20	$62.20	$62.20
7 purchase totals =	$938.69		$1,021.6036	$1,021.60	$1,021.65	$1,021.50