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	$41.87	10.482%	$46.2588	$46.26	$46.25	$46.30
Purchase #2	$178.51	7.303%	$191.5466	$191.55	$191.55	$191.50
Purchase #3	$63.90	10.638%	$70.6977	$70.70	$70.70	$70.70
Purchase #4	$184.33	3.714%	$191.176	$191.18	$191.20	$191.20
Purchase #5	$124.93	13.197%	$141.417	$141.42	$141.40	$141.40
Purchase #6	$127.49	4.153%	$132.7847	$132.78	$132.80	$132.80
Purchase #7	$91.49	5.592%	$96.6061	$96.61	$96.60	$96.60
7 purchase totals =	$812.52		$870.4869	$870.50	$870.50	$870.50