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	$40.35	11.668%	$45.058	$45.06	$45.05	$45.10
Purchase #2	$37.27	12.520%	$41.9362	$41.94	$41.95	$41.90
Purchase #3	$199.92	6.858%	$213.6305	$213.63	$213.65	$213.60
Purchase #4	$129.92	5.564%	$137.1487	$137.15	$137.15	$137.10
Purchase #5	$45.60	8.862%	$49.6411	$49.64	$49.65	$49.60
Purchase #6	$165.55	3.647%	$171.5876	$171.59	$171.60	$171.60
Purchase #7	$236.32	10.276%	$260.6042	$260.60	$260.60	$260.60
7 purchase totals =	$854.93		$919.6063	$919.61	$919.65	$919.50