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	$57.56	6.198%	$61.1276	$61.13	$61.15	$61.10
Purchase #2	$28.56	4.585%	$29.8695	$29.87	$29.85	$29.90
Purchase #3	$137.31	3.381%	$141.9525	$141.95	$141.95	$142.00
Purchase #4	$92.96	3.468%	$96.1839	$96.18	$96.20	$96.20
Purchase #5	$201.92	10.722%	$223.5699	$223.57	$223.55	$223.60
Purchase #6	$29.45	13.679%	$33.4785	$33.48	$33.50	$33.50
Purchase #7	$130.82	8.674%	$142.1673	$142.17	$142.15	$142.20
7 purchase totals =	$678.58		$728.3492	$728.35	$728.35	$728.50