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	$96.76	9.455%	$105.9087	$105.91	$105.90	$105.90
Purchase #2	$159.72	7.741%	$172.0839	$172.08	$172.10	$172.10
Purchase #3	$66.43	7.670%	$71.5252	$71.53	$71.55	$71.50
Purchase #4	$6.67	5.727%	$7.052	$7.05	$7.05	$7.10
Purchase #5	$221.88	12.614%	$249.8679	$249.87	$249.85	$249.90
Purchase #6	$131.34	9.229%	$143.4614	$143.46	$143.45	$143.50
Purchase #7	$172.34	13.620%	$195.8127	$195.81	$195.80	$195.80
7 purchase totals =	$855.14		$945.7118	$945.71	$945.70	$945.80