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	$175.70	13.677%	$199.7305	$199.73	$199.75	$199.70
Purchase #2	$141.77	6.634%	$151.175	$151.18	$151.20	$151.20
Purchase #3	$89.67	12.431%	$100.8169	$100.82	$100.80	$100.80
Purchase #4	$155.37	4.797%	$162.8231	$162.82	$162.80	$162.80
Purchase #5	$242.60	9.382%	$265.3607	$265.36	$265.35	$265.40
Purchase #6	$142.53	5.536%	$150.4205	$150.42	$150.40	$150.40
Purchase #7	$112.82	13.709%	$128.2865	$128.29	$128.30	$128.30
7 purchase totals =	$1,060.46		$1,158.6132	$1,158.62	$1,158.60	$1,158.60