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	$132.90	13.371%	$150.6701	$150.67	$150.65	$150.70
Purchase #2	$64.83	13.635%	$73.6696	$73.67	$73.65	$73.70
Purchase #3	$97.86	4.476%	$102.2402	$102.24	$102.25	$102.20
Purchase #4	$40.68	11.638%	$45.4143	$45.41	$45.40	$45.40
Purchase #5	$81.69	6.457%	$86.9647	$86.96	$86.95	$87.00
Purchase #6	$209.44	6.700%	$223.4725	$223.47	$223.45	$223.50
Purchase #7	$57.91	8.491%	$62.8271	$62.83	$62.85	$62.80
7 purchase totals =	$685.31		$745.2585	$745.25	$745.20	$745.30