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	$237.81	7.536%	$255.7314	$255.73	$255.75	$255.70
Purchase #2	$186.73	13.406%	$211.763	$211.76	$211.75	$211.80
Purchase #3	$126.76	11.522%	$141.3653	$141.37	$141.35	$141.40
Purchase #4	$45.36	6.779%	$48.435	$48.44	$48.45	$48.40
Purchase #5	$101.50	7.156%	$108.7633	$108.76	$108.75	$108.80
Purchase #6	$42.67	11.520%	$47.5856	$47.59	$47.60	$47.60
Purchase #7	$180.45	5.351%	$190.1059	$190.11	$190.10	$190.10
7 purchase totals =	$921.28		$1,003.7495	$1,003.76	$1,003.75	$1,003.80