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	$244.25	6.691%	$260.5928	$260.59	$260.60	$260.60
Purchase #2	$42.95	7.505%	$46.1734	$46.17	$46.15	$46.20
Purchase #3	$235.44	8.555%	$255.5819	$255.58	$255.60	$255.60
Purchase #4	$121.46	12.700%	$136.8854	$136.89	$136.90	$136.90
Purchase #5	$119.50	6.828%	$127.6595	$127.66	$127.65	$127.70
Purchase #6	$186.49	3.124%	$192.3159	$192.32	$192.30	$192.30
Purchase #7	$33.31	12.515%	$37.4787	$37.48	$37.50	$37.50
7 purchase totals =	$983.40		$1,056.6876	$1,056.69	$1,056.70	$1,056.80