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	$34.57	8.235%	$37.4168	$37.42	$37.40	$37.40
Purchase #2	$138.51	3.541%	$143.4146	$143.41	$143.40	$143.40
Purchase #3	$95.79	10.434%	$105.7847	$105.78	$105.80	$105.80
Purchase #4	$172.70	11.275%	$192.1719	$192.17	$192.15	$192.20
Purchase #5	$38.26	10.868%	$42.4181	$42.42	$42.40	$42.40
Purchase #6	$162.82	11.801%	$182.0344	$182.03	$182.05	$182.00
Purchase #7	$98.67	5.696%	$104.2902	$104.29	$104.30	$104.30
7 purchase totals =	$741.32		$807.5307	$807.52	$807.50	$807.50