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	$131.66	11.865%	$147.2815	$147.28	$147.30	$147.30
Purchase #2	$136.51	11.505%	$152.2155	$152.22	$152.20	$152.20
Purchase #3	$103.28	7.588%	$111.1169	$111.12	$111.10	$111.10
Purchase #4	$72.44	5.352%	$76.317	$76.32	$76.30	$76.30
Purchase #5	$52.72	10.610%	$58.3136	$58.31	$58.30	$58.30
Purchase #6	$92.94	13.821%	$105.7852	$105.79	$105.80	$105.80
Purchase #7	$214.48	12.443%	$241.1677	$241.17	$241.15	$241.20
7 purchase totals =	$804.03		$892.1974	$892.21	$892.15	$892.20