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	$60.25	10.470%	$66.5582	$66.56	$66.55	$66.60
Purchase #2	$53.91	13.682%	$61.286	$61.29	$61.30	$61.30
Purchase #3	$179.65	9.625%	$196.9413	$196.94	$196.95	$196.90
Purchase #4	$24.29	8.725%	$26.4093	$26.41	$26.40	$26.40
Purchase #5	$134.85	7.777%	$145.3373	$145.34	$145.35	$145.30
Purchase #6	$127.58	11.668%	$142.466	$142.47	$142.45	$142.50
Purchase #7	$215.64	3.145%	$222.4219	$222.42	$222.40	$222.40
7 purchase totals =	$796.17		$861.4200	$861.43	$861.40	$861.40