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	$162.72	4.557%	$170.1352	$170.14	$170.15	$170.10
Purchase #2	$155.57	10.585%	$172.0371	$172.04	$172.05	$172.00
Purchase #3	$114.49	13.631%	$130.0961	$130.10	$130.10	$130.10
Purchase #4	$243.30	5.184%	$255.9127	$255.91	$255.90	$255.90
Purchase #5	$208.74	3.387%	$215.81	$215.81	$215.80	$215.80
Purchase #6	$56.76	8.297%	$61.4694	$61.47	$61.45	$61.50
Purchase #7	$144.68	4.384%	$151.0228	$151.02	$151.00	$151.00
7 purchase totals =	$1,086.26		$1,156.4833	$1,156.49	$1,156.45	$1,156.40