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	$124.67	12.791%	$140.6165	$140.62	$140.60	$140.60
Purchase #2	$161.97	4.437%	$169.1566	$169.16	$169.15	$169.20
Purchase #3	$67.27	13.523%	$76.3669	$76.37	$76.35	$76.40
Purchase #4	$243.78	8.233%	$263.8504	$263.85	$263.85	$263.90
Purchase #5	$29.75	8.108%	$32.1621	$32.16	$32.15	$32.20
Purchase #6	$247.36	3.607%	$256.2823	$256.28	$256.30	$256.30
Purchase #7	$101.78	9.378%	$111.3249	$111.32	$111.30	$111.30
7 purchase totals =	$976.58		$1,049.7597	$1,049.76	$1,049.70	$1,049.90