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	$121.25	9.287%	$132.5105	$132.51	$132.50	$132.50
Purchase #2	$152.43	13.686%	$173.2916	$173.29	$173.30	$173.30
Purchase #3	$233.32	10.102%	$256.89	$256.89	$256.90	$256.90
Purchase #4	$55.62	7.678%	$59.8905	$59.89	$59.90	$59.90
Purchase #5	$197.34	8.107%	$213.3384	$213.34	$213.35	$213.30
Purchase #6	$65.98	7.520%	$70.9417	$70.94	$70.95	$70.90
Purchase #7	$227.89	10.423%	$251.643	$251.64	$251.65	$251.60
7 purchase totals =	$1,053.83		$1,158.5057	$1,158.50	$1,158.55	$1,158.40