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	$227.90	9.317%	$249.1334	$249.13	$249.15	$249.10
Purchase #2	$36.72	11.762%	$41.039	$41.04	$41.05	$41.00
Purchase #3	$215.47	3.581%	$223.186	$223.19	$223.20	$223.20
Purchase #4	$184.41	4.620%	$192.9297	$192.93	$192.95	$192.90
Purchase #5	$236.56	7.723%	$254.8295	$254.83	$254.85	$254.80
Purchase #6	$158.25	10.206%	$174.401	$174.40	$174.40	$174.40
Purchase #7	$13.60	9.460%	$14.8866	$14.89	$14.90	$14.90
7 purchase totals =	$1,072.91		$1,150.4052	$1,150.41	$1,150.50	$1,150.30