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	$139.27	7.295%	$149.4297	$149.43	$149.45	$149.40
Purchase #2	$229.79	5.638%	$242.7456	$242.75	$242.75	$242.70
Purchase #3	$173.78	9.260%	$189.872	$189.87	$189.85	$189.90
Purchase #4	$26.47	13.755%	$30.1109	$30.11	$30.10	$30.10
Purchase #5	$91.41	10.182%	$100.7174	$100.72	$100.70	$100.70
Purchase #6	$103.63	7.863%	$111.7784	$111.78	$111.80	$111.80
Purchase #7	$57.87	11.245%	$64.3775	$64.38	$64.40	$64.40
7 purchase totals =	$822.22		$889.0315	$889.04	$889.05	$889.00