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	$186.27	7.278%	$199.8267	$199.83	$199.85	$199.80
Purchase #2	$197.83	10.484%	$218.5705	$218.57	$218.55	$218.60
Purchase #3	$66.47	13.181%	$75.2314	$75.23	$75.25	$75.20
Purchase #4	$159.34	12.820%	$179.7674	$179.77	$179.75	$179.80
Purchase #5	$83.95	7.812%	$90.5082	$90.51	$90.50	$90.50
Purchase #6	$223.29	13.392%	$253.193	$253.19	$253.20	$253.20
Purchase #7	$133.72	5.317%	$140.8299	$140.83	$140.85	$140.80
7 purchase totals =	$1,050.87		$1,157.9271	$1,157.93	$1,157.95	$1,157.90