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	$78.63	10.432%	$86.8327	$86.83	$86.85	$86.80
Purchase #2	$123.71	10.871%	$137.1585	$137.16	$137.15	$137.20
Purchase #3	$130.31	12.459%	$146.5453	$146.55	$146.55	$146.50
Purchase #4	$44.52	9.850%	$48.9052	$48.91	$48.90	$48.90
Purchase #5	$150.39	13.135%	$170.1437	$170.14	$170.15	$170.10
Purchase #6	$111.96	6.829%	$119.6057	$119.61	$119.60	$119.60
Purchase #7	$227.39	12.677%	$256.2162	$256.22	$256.20	$256.20
7 purchase totals =	$866.91		$965.4073	$965.42	$965.40	$965.30