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	$123.32	6.505%	$131.342	$131.34	$131.35	$131.30
Purchase #2	$48.64	3.393%	$50.2904	$50.29	$50.30	$50.30
Purchase #3	$118.84	10.515%	$131.336	$131.34	$131.35	$131.30
Purchase #4	$144.57	10.130%	$159.2149	$159.21	$159.20	$159.20
Purchase #5	$161.85	8.771%	$176.0459	$176.05	$176.05	$176.00
Purchase #6	$99.37	4.255%	$103.5982	$103.60	$103.60	$103.60
Purchase #7	$147.65	8.854%	$160.7229	$160.72	$160.70	$160.70
7 purchase totals =	$844.24		$912.5503	$912.55	$912.55	$912.40