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	$44.88	12.707%	$50.5829	$50.58	$50.60	$50.60
Purchase #2	$217.93	12.694%	$245.594	$245.59	$245.60	$245.60
Purchase #3	$29.71	5.868%	$31.4534	$31.45	$31.45	$31.50
Purchase #4	$42.76	5.357%	$45.0507	$45.05	$45.05	$45.10
Purchase #5	$41.78	10.304%	$46.085	$46.09	$46.10	$46.10
Purchase #6	$71.36	3.143%	$73.6028	$73.60	$73.60	$73.60
Purchase #7	$247.96	3.544%	$256.7477	$256.75	$256.75	$256.70
7 purchase totals =	$696.38		$749.1165	$749.11	$749.15	$749.20