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	$198.77	13.208%	$225.0235	$225.02	$225.00	$225.00
Purchase #2	$246.39	10.502%	$272.2659	$272.27	$272.25	$272.30
Purchase #3	$21.75	6.764%	$23.2212	$23.22	$23.20	$23.20
Purchase #4	$36.45	5.560%	$38.4766	$38.48	$38.50	$38.50
Purchase #5	$135.83	13.602%	$154.3056	$154.31	$154.30	$154.30
Purchase #6	$218.64	6.633%	$233.1424	$233.14	$233.15	$233.10
Purchase #7	$192.76	6.590%	$205.4629	$205.46	$205.45	$205.50
7 purchase totals =	$1,050.59		$1,151.8981	$1,151.90	$1,151.85	$1,151.90