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	$72.32	6.813%	$77.2472	$77.25	$77.25	$77.20
Purchase #2	$125.97	4.536%	$131.684	$131.68	$131.70	$131.70
Purchase #3	$94.32	6.638%	$100.581	$100.58	$100.60	$100.60
Purchase #4	$62.27	4.500%	$65.0722	$65.07	$65.05	$65.10
Purchase #5	$29.27	12.487%	$32.9249	$32.92	$32.90	$32.90
Purchase #6	$44.31	9.669%	$48.5943	$48.59	$48.60	$48.60
Purchase #7	$5.74	8.588%	$6.233	$6.23	$6.25	$6.20
7 purchase totals =	$434.20		$462.3366	$462.32	$462.35	$462.30