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	$58.43	4.709%	$61.1815	$61.18	$61.20	$61.20
Purchase #2	$126.78	3.680%	$131.4455	$131.45	$131.45	$131.40
Purchase #3	$226.27	11.323%	$251.8906	$251.89	$251.90	$251.90
Purchase #4	$221.95	11.861%	$248.2755	$248.28	$248.30	$248.30
Purchase #5	$139.57	8.221%	$151.044	$151.04	$151.05	$151.00
Purchase #6	$63.47	11.820%	$70.9722	$70.97	$70.95	$71.00
Purchase #7	$53.42	6.118%	$56.6882	$56.69	$56.70	$56.70
7 purchase totals =	$889.89		$971.4975	$971.50	$971.55	$971.50