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	$215.42	13.141%	$243.7283	$243.73	$243.75	$243.70
Purchase #2	$231.27	13.465%	$262.4105	$262.41	$262.40	$262.40
Purchase #3	$242.46	4.329%	$252.9561	$252.96	$252.95	$253.00
Purchase #4	$98.62	11.248%	$109.7128	$109.71	$109.70	$109.70
Purchase #5	$211.94	12.743%	$238.9475	$238.95	$238.95	$238.90
Purchase #6	$59.47	4.873%	$62.368	$62.37	$62.35	$62.40
Purchase #7	$212.65	13.475%	$241.3046	$241.30	$241.30	$241.30
7 purchase totals =	$1,271.83		$1,411.4278	$1,411.43	$1,411.40	$1,411.40