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	$26.30	6.256%	$27.9453	$27.95	$27.95	$27.90
Purchase #2	$229.70	11.690%	$256.5519	$256.55	$256.55	$256.60
Purchase #3	$127.95	6.682%	$136.4996	$136.50	$136.50	$136.50
Purchase #4	$88.35	12.519%	$99.4105	$99.41	$99.40	$99.40
Purchase #5	$212.47	4.499%	$222.029	$222.03	$222.05	$222.00
Purchase #6	$150.91	3.536%	$156.2462	$156.25	$156.25	$156.20
Purchase #7	$153.98	7.703%	$165.8411	$165.84	$165.85	$165.80
7 purchase totals =	$989.66		$1,064.5236	$1,064.53	$1,064.55	$1,064.40