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	$199.67	8.373%	$216.3884	$216.39	$216.40	$216.40
Purchase #2	$246.30	12.430%	$276.9151	$276.92	$276.90	$276.90
Purchase #3	$196.78	10.784%	$218.0008	$218.00	$218.00	$218.00
Purchase #4	$65.85	7.388%	$70.715	$70.72	$70.70	$70.70
Purchase #5	$66.45	8.507%	$72.1029	$72.10	$72.10	$72.10
Purchase #6	$20.51	6.680%	$21.8801	$21.88	$21.90	$21.90
Purchase #7	$136.29	10.480%	$150.5732	$150.57	$150.55	$150.60
7 purchase totals =	$931.85		$1,026.5755	$1,026.58	$1,026.55	$1,026.60