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	$234.95	12.481%	$264.2741	$264.27	$264.25	$264.30
Purchase #2	$242.75	6.873%	$259.4342	$259.43	$259.45	$259.40
Purchase #3	$40.77	11.515%	$45.4647	$45.46	$45.45	$45.50
Purchase #4	$58.50	13.125%	$66.1781	$66.18	$66.20	$66.20
Purchase #5	$50.60	4.286%	$52.7687	$52.77	$52.75	$52.80
Purchase #6	$36.84	12.263%	$41.3577	$41.36	$41.35	$41.40
Purchase #7	$244.60	8.568%	$265.5573	$265.56	$265.55	$265.60
7 purchase totals =	$909.01		$995.0348	$995.03	$995.00	$995.20