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	$210.39	7.383%	$225.9231	$225.92	$225.90	$225.90
Purchase #2	$205.30	13.226%	$232.453	$232.45	$232.45	$232.50
Purchase #3	$146.33	4.766%	$153.3041	$153.30	$153.30	$153.30
Purchase #4	$59.30	12.330%	$66.6117	$66.61	$66.60	$66.60
Purchase #5	$67.25	4.638%	$70.3691	$70.37	$70.35	$70.40
Purchase #6	$205.60	8.318%	$222.7018	$222.70	$222.70	$222.70
Purchase #7	$136.32	7.816%	$146.9748	$146.97	$146.95	$147.00
7 purchase totals =	$1,030.49		$1,118.3376	$1,118.32	$1,118.25	$1,118.40