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	$86.86	9.700%	$95.2854	$95.29	$95.30	$95.30
Purchase #2	$95.26	10.390%	$105.1575	$105.16	$105.15	$105.20
Purchase #3	$233.72	4.551%	$244.3566	$244.36	$244.35	$244.40
Purchase #4	$61.45	10.155%	$67.6902	$67.69	$67.70	$67.70
Purchase #5	$11.60	10.592%	$12.8287	$12.83	$12.85	$12.80
Purchase #6	$55.47	6.125%	$58.8675	$58.87	$58.85	$58.90
Purchase #7	$125.40	11.256%	$139.515	$139.52	$139.50	$139.50
7 purchase totals =	$669.76		$723.7009	$723.72	$723.70	$723.80