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	$55.83	11.684%	$62.3532	$62.35	$62.35	$62.40
Purchase #2	$34.54	5.357%	$36.3903	$36.39	$36.40	$36.40
Purchase #3	$196.43	13.282%	$222.5198	$222.52	$222.50	$222.50
Purchase #4	$206.86	8.549%	$224.5445	$224.54	$224.55	$224.50
Purchase #5	$82.54	11.244%	$91.8208	$91.82	$91.80	$91.80
Purchase #6	$105.62	11.619%	$117.892	$117.89	$117.90	$117.90
Purchase #7	$215.74	12.505%	$242.7183	$242.72	$242.70	$242.70
7 purchase totals =	$897.56		$998.2389	$998.23	$998.20	$998.20