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	$88.63	13.541%	$100.6314	$100.63	$100.65	$100.60
Purchase #2	$100.62	10.753%	$111.4397	$111.44	$111.45	$111.40
Purchase #3	$232.64	4.691%	$243.5531	$243.55	$243.55	$243.60
Purchase #4	$109.53	12.763%	$123.5093	$123.51	$123.50	$123.50
Purchase #5	$87.32	3.249%	$90.157	$90.16	$90.15	$90.20
Purchase #6	$75.53	9.813%	$82.9418	$82.94	$82.95	$82.90
Purchase #7	$196.84	8.459%	$213.4907	$213.49	$213.50	$213.50
7 purchase totals =	$891.11		$965.7230	$965.72	$965.75	$965.70