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	$56.30	5.649%	$59.4804	$59.48	$59.50	$59.50
Purchase #2	$33.30	8.588%	$36.1598	$36.16	$36.15	$36.20
Purchase #3	$182.82	7.220%	$196.0196	$196.02	$196.00	$196.00
Purchase #4	$12.42	9.226%	$13.5659	$13.57	$13.55	$13.60
Purchase #5	$102.95	8.735%	$111.9427	$111.94	$111.95	$111.90
Purchase #6	$32.74	13.327%	$37.1033	$37.10	$37.10	$37.10
Purchase #7	$11.63	9.231%	$12.7036	$12.70	$12.70	$12.70
7 purchase totals =	$432.16		$466.9753	$466.97	$466.95	$467.00