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	$71.56	6.496%	$76.2085	$76.21	$76.20	$76.20
Purchase #2	$55.50	7.849%	$59.8562	$59.86	$59.85	$59.90
Purchase #3	$209.41	4.701%	$219.2544	$219.25	$219.25	$219.30
Purchase #4	$198.54	11.102%	$220.5819	$220.58	$220.60	$220.60
Purchase #5	$180.94	9.701%	$198.493	$198.49	$198.50	$198.50
Purchase #6	$232.62	9.847%	$255.5261	$255.53	$255.55	$255.50
Purchase #7	$114.78	3.691%	$119.0165	$119.02	$119.00	$119.00
7 purchase totals =	$1,063.35		$1,148.9366	$1,148.94	$1,148.95	$1,149.00