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	$7.49	7.437%	$8.047	$8.05	$8.05	$8.00
Purchase #2	$190.57	13.660%	$216.6019	$216.60	$216.60	$216.60
Purchase #3	$143.75	4.749%	$150.5767	$150.58	$150.60	$150.60
Purchase #4	$140.91	13.492%	$159.9216	$159.92	$159.90	$159.90
Purchase #5	$111.86	10.496%	$123.6008	$123.60	$123.60	$123.60
Purchase #6	$221.34	13.306%	$250.7915	$250.79	$250.80	$250.80
Purchase #7	$178.54	13.678%	$202.9607	$202.96	$202.95	$203.00
7 purchase totals =	$994.46		$1,112.5002	$1,112.50	$1,112.50	$1,112.50