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	$188.85	4.162%	$196.7099	$196.71	$196.70	$196.70
Purchase #2	$216.81	5.427%	$228.5763	$228.58	$228.60	$228.60
Purchase #3	$166.98	8.282%	$180.8093	$180.81	$180.80	$180.80
Purchase #4	$176.71	13.835%	$201.1578	$201.16	$201.15	$201.20
Purchase #5	$147.76	11.753%	$165.1262	$165.13	$165.15	$165.10
Purchase #6	$6.79	11.373%	$7.5622	$7.56	$7.55	$7.60
Purchase #7	$86.57	10.446%	$95.6131	$95.61	$95.60	$95.60
7 purchase totals =	$990.47		$1,075.5548	$1,075.56	$1,075.55	$1,075.60