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	$198.39	6.303%	$210.8945	$210.89	$210.90	$210.90
Purchase #2	$214.71	12.352%	$241.231	$241.23	$241.25	$241.20
Purchase #3	$55.42	12.550%	$62.3752	$62.38	$62.40	$62.40
Purchase #4	$238.73	3.626%	$247.3863	$247.39	$247.40	$247.40
Purchase #5	$226.47	5.223%	$238.2985	$238.30	$238.30	$238.30
Purchase #6	$223.48	6.444%	$237.8811	$237.88	$237.90	$237.90
Purchase #7	$6.95	8.472%	$7.5388	$7.54	$7.55	$7.50
7 purchase totals =	$1,164.15		$1,245.6054	$1,245.61	$1,245.70	$1,245.60