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	$212.54	3.454%	$219.8811	$219.88	$219.90	$219.90
Purchase #2	$235.50	5.466%	$248.3724	$248.37	$248.35	$248.40
Purchase #3	$113.72	11.250%	$126.5135	$126.51	$126.50	$126.50
Purchase #4	$58.58	10.438%	$64.6946	$64.69	$64.70	$64.70
Purchase #5	$108.91	9.172%	$118.8992	$118.90	$118.90	$118.90
Purchase #6	$132.68	5.111%	$139.4613	$139.46	$139.45	$139.50
Purchase #7	$73.56	7.317%	$78.9424	$78.94	$78.95	$78.90
7 purchase totals =	$935.49		$996.7645	$996.75	$996.75	$996.80