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	$111.80	9.683%	$122.6256	$122.63	$122.65	$122.60
Purchase #2	$120.71	12.873%	$136.249	$136.25	$136.25	$136.20
Purchase #3	$72.44	13.663%	$82.3375	$82.34	$82.35	$82.30
Purchase #4	$144.53	5.324%	$152.2248	$152.22	$152.20	$152.20
Purchase #5	$186.42	4.489%	$194.7884	$194.79	$194.80	$194.80
Purchase #6	$65.99	8.321%	$71.481	$71.48	$71.50	$71.50
Purchase #7	$153.70	9.700%	$168.6089	$168.61	$168.60	$168.60
7 purchase totals =	$855.59		$928.3152	$928.32	$928.35	$928.20