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	$59.30	3.156%	$61.1715	$61.17	$61.15	$61.20
Purchase #2	$201.32	12.403%	$226.2897	$226.29	$226.30	$226.30
Purchase #3	$244.66	6.178%	$259.7751	$259.78	$259.80	$259.80
Purchase #4	$171.67	8.266%	$185.8602	$185.86	$185.85	$185.90
Purchase #5	$126.83	9.203%	$138.5022	$138.50	$138.50	$138.50
Purchase #6	$105.73	10.467%	$116.7968	$116.80	$116.80	$116.80
Purchase #7	$144.83	5.171%	$152.3192	$152.32	$152.30	$152.30
7 purchase totals =	$1,054.34		$1,140.7147	$1,140.72	$1,140.70	$1,140.80