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	$67.30	5.665%	$71.1125	$71.11	$71.10	$71.10
Purchase #2	$6.64	7.226%	$7.1198	$7.12	$7.10	$7.10
Purchase #3	$235.38	5.173%	$247.5562	$247.56	$247.55	$247.60
Purchase #4	$21.61	4.805%	$22.6484	$22.65	$22.65	$22.60
Purchase #5	$59.31	3.575%	$61.4303	$61.43	$61.45	$61.40
Purchase #6	$35.49	6.615%	$37.8377	$37.84	$37.85	$37.80
Purchase #7	$53.40	10.572%	$59.0454	$59.05	$59.05	$59.00
7 purchase totals =	$479.13		$506.7503	$506.76	$506.75	$506.60