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	$245.53	4.505%	$256.5911	$256.59	$256.60	$256.60
Purchase #2	$134.50	13.365%	$152.4759	$152.48	$152.50	$152.50
Purchase #3	$38.60	11.844%	$43.1718	$43.17	$43.15	$43.20
Purchase #4	$231.38	10.188%	$254.953	$254.95	$254.95	$255.00
Purchase #5	$151.99	3.367%	$157.1075	$157.11	$157.10	$157.10
Purchase #6	$29.84	9.284%	$32.6103	$32.61	$32.60	$32.60
Purchase #7	$88.66	10.590%	$98.0491	$98.05	$98.05	$98.00
7 purchase totals =	$920.50		$994.9587	$994.96	$994.95	$995.00