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	$211.61	10.697%	$234.2459	$234.25	$234.25	$234.20
Purchase #2	$79.42	4.344%	$82.87	$82.87	$82.85	$82.90
Purchase #3	$30.69	13.632%	$34.8737	$34.87	$34.85	$34.90
Purchase #4	$6.91	9.709%	$7.5809	$7.58	$7.60	$7.60
Purchase #5	$75.54	10.616%	$83.5593	$83.56	$83.55	$83.60
Purchase #6	$155.60	11.518%	$173.522	$173.52	$173.50	$173.50
Purchase #7	$241.89	12.844%	$272.9584	$272.96	$272.95	$273.00
7 purchase totals =	$801.66		$889.6102	$889.61	$889.55	$889.70