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	$208.98	11.638%	$233.3011	$233.30	$233.30	$233.30
Purchase #2	$34.99	7.630%	$37.6597	$37.66	$37.65	$37.70
Purchase #3	$132.60	11.365%	$147.67	$147.67	$147.65	$147.70
Purchase #4	$85.46	5.571%	$90.221	$90.22	$90.20	$90.20
Purchase #5	$69.78	10.769%	$77.2946	$77.29	$77.30	$77.30
Purchase #6	$152.44	9.117%	$166.338	$166.34	$166.35	$166.30
Purchase #7	$13.49	4.475%	$14.0937	$14.09	$14.10	$14.10
7 purchase totals =	$697.74		$766.5781	$766.57	$766.55	$766.60