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	$60.36	4.408%	$63.0207	$63.02	$63.00	$63.00
Purchase #2	$39.35	8.251%	$42.5968	$42.60	$42.60	$42.60
Purchase #3	$123.77	6.564%	$131.8943	$131.89	$131.90	$131.90
Purchase #4	$16.48	13.698%	$18.7374	$18.74	$18.75	$18.70
Purchase #5	$9.65	5.391%	$10.1702	$10.17	$10.15	$10.20
Purchase #6	$147.42	5.389%	$155.3645	$155.36	$155.35	$155.40
Purchase #7	$30.61	9.669%	$33.5697	$33.57	$33.55	$33.60
7 purchase totals =	$427.64		$455.3536	$455.35	$455.30	$455.40