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	$184.32	6.435%	$196.181	$196.18	$196.20	$196.20
Purchase #2	$233.79	9.338%	$255.6213	$255.62	$255.60	$255.60
Purchase #3	$136.84	13.707%	$155.5967	$155.60	$155.60	$155.60
Purchase #4	$198.58	10.197%	$218.8292	$218.83	$218.85	$218.80
Purchase #5	$135.88	6.451%	$144.6456	$144.65	$144.65	$144.60
Purchase #6	$115.81	3.832%	$120.2478	$120.25	$120.25	$120.20
Purchase #7	$32.96	9.862%	$36.2105	$36.21	$36.20	$36.20
7 purchase totals =	$1,038.18		$1,127.3321	$1,127.34	$1,127.35	$1,127.20