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	$215.64	7.204%	$231.1747	$231.17	$231.15	$231.20
Purchase #2	$182.63	4.491%	$190.8319	$190.83	$190.85	$190.80
Purchase #3	$32.70	7.367%	$35.109	$35.11	$35.10	$35.10
Purchase #4	$91.97	7.803%	$99.1464	$99.15	$99.15	$99.10
Purchase #5	$235.45	13.429%	$267.0686	$267.07	$267.05	$267.10
Purchase #6	$151.44	11.460%	$168.795	$168.80	$168.80	$168.80
Purchase #7	$33.59	13.516%	$38.13	$38.13	$38.15	$38.10
7 purchase totals =	$943.42		$1,030.2556	$1,030.26	$1,030.25	$1,030.20