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	$196.41	6.178%	$208.5442	$208.54	$208.55	$208.50
Purchase #2	$156.55	5.538%	$165.2197	$165.22	$165.20	$165.20
Purchase #3	$11.91	3.369%	$12.3112	$12.31	$12.30	$12.30
Purchase #4	$100.46	11.454%	$111.9667	$111.97	$111.95	$112.00
Purchase #5	$105.25	5.817%	$111.3724	$111.37	$111.35	$111.40
Purchase #6	$72.62	3.603%	$75.2365	$75.24	$75.25	$75.20
Purchase #7	$157.29	8.522%	$170.6943	$170.69	$170.70	$170.70
7 purchase totals =	$800.49		$855.3450	$855.34	$855.30	$855.30