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	$133.91	4.297%	$139.6641	$139.66	$139.65	$139.70
Purchase #2	$137.98	5.206%	$145.1632	$145.16	$145.15	$145.20
Purchase #3	$130.94	9.538%	$143.4291	$143.43	$143.45	$143.40
Purchase #4	$235.54	7.458%	$253.1066	$253.11	$253.10	$253.10
Purchase #5	$133.83	13.505%	$151.9037	$151.90	$151.90	$151.90
Purchase #6	$161.60	10.523%	$178.6052	$178.61	$178.60	$178.60
Purchase #7	$82.44	8.206%	$89.205	$89.21	$89.20	$89.20
7 purchase totals =	$1,016.24		$1,101.0769	$1,101.08	$1,101.05	$1,101.10