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	$113.75	11.833%	$127.21	$127.21	$127.20	$127.20
Purchase #2	$139.54	9.678%	$153.0447	$153.04	$153.05	$153.00
Purchase #3	$99.98	11.564%	$111.5417	$111.54	$111.55	$111.50
Purchase #4	$99.50	8.398%	$107.856	$107.86	$107.85	$107.90
Purchase #5	$72.73	13.422%	$82.4918	$82.49	$82.50	$82.50
Purchase #6	$73.95	12.419%	$83.1339	$83.13	$83.15	$83.10
Purchase #7	$221.43	3.652%	$229.5166	$229.52	$229.50	$229.50
7 purchase totals =	$820.88		$894.7947	$894.79	$894.80	$894.70