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	$135.61	12.642%	$152.7538	$152.75	$152.75	$152.80
Purchase #2	$125.46	10.660%	$138.834	$138.83	$138.85	$138.80
Purchase #3	$93.86	4.184%	$97.7871	$97.79	$97.80	$97.80
Purchase #4	$159.69	13.801%	$181.7288	$181.73	$181.75	$181.70
Purchase #5	$120.69	6.795%	$128.8909	$128.89	$128.90	$128.90
Purchase #6	$139.81	8.378%	$151.5233	$151.52	$151.50	$151.50
Purchase #7	$91.67	11.208%	$101.9444	$101.94	$101.95	$101.90
7 purchase totals =	$866.79		$953.4623	$953.45	$953.50	$953.40