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	$209.37	6.483%	$222.9435	$222.94	$222.95	$222.90
Purchase #2	$230.88	12.588%	$259.9432	$259.94	$259.95	$259.90
Purchase #3	$185.30	11.427%	$206.4742	$206.47	$206.45	$206.50
Purchase #4	$85.30	9.457%	$93.3668	$93.37	$93.35	$93.40
Purchase #5	$56.35	4.743%	$59.0227	$59.02	$59.00	$59.00
Purchase #6	$26.67	12.243%	$29.9352	$29.94	$29.95	$29.90
Purchase #7	$99.44	9.300%	$108.6879	$108.69	$108.70	$108.70
7 purchase totals =	$893.31		$980.3735	$980.37	$980.35	$980.30