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	$192.77	11.766%	$215.4513	$215.45	$215.45	$215.50
Purchase #2	$69.82	4.296%	$72.8195	$72.82	$72.80	$72.80
Purchase #3	$246.45	11.211%	$274.0795	$274.08	$274.10	$274.10
Purchase #4	$162.93	11.397%	$181.4991	$181.50	$181.50	$181.50
Purchase #5	$250.48	13.342%	$283.899	$283.90	$283.90	$283.90
Purchase #6	$236.47	8.501%	$256.5723	$256.57	$256.55	$256.60
Purchase #7	$164.51	3.411%	$170.1214	$170.12	$170.10	$170.10
7 purchase totals =	$1,323.43		$1,454.4421	$1,454.44	$1,454.40	$1,454.50