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	$147.80	7.238%	$158.4978	$158.50	$158.50	$158.50
Purchase #2	$57.89	3.578%	$59.9613	$59.96	$59.95	$60.00
Purchase #3	$143.38	10.189%	$157.989	$157.99	$158.00	$158.00
Purchase #4	$203.78	13.538%	$231.3677	$231.37	$231.35	$231.40
Purchase #5	$237.86	7.425%	$255.5211	$255.52	$255.50	$255.50
Purchase #6	$85.82	7.664%	$92.3972	$92.40	$92.40	$92.40
Purchase #7	$216.56	13.785%	$246.4128	$246.41	$246.40	$246.40
7 purchase totals =	$1,093.09		$1,202.1469	$1,202.15	$1,202.10	$1,202.20