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	$92.81	9.658%	$101.7736	$101.77	$101.75	$101.80
Purchase #2	$146.89	6.223%	$156.031	$156.03	$156.05	$156.00
Purchase #3	$34.78	7.198%	$37.2835	$37.28	$37.30	$37.30
Purchase #4	$37.82	7.706%	$40.7344	$40.73	$40.75	$40.70
Purchase #5	$209.34	8.624%	$227.3935	$227.39	$227.40	$227.40
Purchase #6	$75.25	8.784%	$81.86	$81.86	$81.85	$81.90
Purchase #7	$233.52	8.651%	$253.7218	$253.72	$253.70	$253.70
7 purchase totals =	$830.41		$898.7978	$898.78	$898.80	$898.80