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	$85.56	8.126%	$92.5126	$92.51	$92.50	$92.50
Purchase #2	$36.96	6.148%	$39.2323	$39.23	$39.25	$39.20
Purchase #3	$36.85	10.333%	$40.6577	$40.66	$40.65	$40.70
Purchase #4	$11.44	8.662%	$12.4309	$12.43	$12.45	$12.40
Purchase #5	$143.25	11.220%	$159.3227	$159.32	$159.30	$159.30
Purchase #6	$164.88	5.762%	$174.3804	$174.38	$174.40	$174.40
Purchase #7	$96.54	8.726%	$104.9641	$104.96	$104.95	$105.00
7 purchase totals =	$575.48		$623.5007	$623.49	$623.50	$623.50