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	$212.41	5.130%	$223.3066	$223.31	$223.30	$223.30
Purchase #2	$74.25	3.476%	$76.8309	$76.83	$76.85	$76.80
Purchase #3	$147.59	7.748%	$159.0253	$159.03	$159.05	$159.00
Purchase #4	$50.34	6.447%	$53.5854	$53.59	$53.60	$53.60
Purchase #5	$32.82	13.148%	$37.1352	$37.14	$37.15	$37.10
Purchase #6	$198.90	13.659%	$226.0678	$226.07	$226.05	$226.10
Purchase #7	$199.42	13.155%	$225.6537	$225.65	$225.65	$225.70
7 purchase totals =	$915.73		$1,001.6049	$1,001.62	$1,001.65	$1,001.60