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	$185.59	7.624%	$199.7394	$199.74	$199.75	$199.70
Purchase #2	$24.77	11.583%	$27.6391	$27.64	$27.65	$27.60
Purchase #3	$217.71	12.829%	$245.64	$245.64	$245.65	$245.60
Purchase #4	$40.47	13.299%	$45.8521	$45.85	$45.85	$45.90
Purchase #5	$80.35	11.244%	$89.3846	$89.38	$89.40	$89.40
Purchase #6	$37.70	9.717%	$41.3633	$41.36	$41.35	$41.40
Purchase #7	$186.33	6.733%	$198.8756	$198.88	$198.90	$198.90
7 purchase totals =	$772.92		$848.4941	$848.49	$848.55	$848.50