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	$96.32	5.784%	$101.8911	$101.89	$101.90	$101.90
Purchase #2	$20.51	8.299%	$22.2121	$22.21	$22.20	$22.20
Purchase #3	$36.66	4.434%	$38.2855	$38.29	$38.30	$38.30
Purchase #4	$70.35	11.700%	$78.581	$78.58	$78.60	$78.60
Purchase #5	$242.72	7.676%	$261.3512	$261.35	$261.35	$261.40
Purchase #6	$79.95	8.773%	$86.964	$86.96	$86.95	$87.00
Purchase #7	$149.41	10.848%	$165.618	$165.62	$165.60	$165.60
7 purchase totals =	$695.92		$754.9029	$754.90	$754.90	$755.00