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	$37.29	8.341%	$40.4004	$40.40	$40.40	$40.40
Purchase #2	$203.88	5.525%	$215.1444	$215.14	$215.15	$215.10
Purchase #3	$40.50	11.250%	$45.0563	$45.06	$45.05	$45.10
Purchase #4	$95.57	4.142%	$99.5285	$99.53	$99.55	$99.50
Purchase #5	$129.95	13.228%	$147.1398	$147.14	$147.15	$147.10
Purchase #6	$250.67	10.569%	$277.1633	$277.16	$277.15	$277.20
Purchase #7	$117.63	12.106%	$131.8703	$131.87	$131.85	$131.90
7 purchase totals =	$875.49		$956.3030	$956.30	$956.30	$956.30