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	$32.98	13.510%	$37.4356	$37.44	$37.45	$37.40
Purchase #2	$179.29	11.214%	$199.3956	$199.40	$199.40	$199.40
Purchase #3	$172.55	11.136%	$191.7652	$191.77	$191.75	$191.80
Purchase #4	$136.52	10.714%	$151.1468	$151.15	$151.15	$151.10
Purchase #5	$39.99	13.787%	$45.5034	$45.50	$45.50	$45.50
Purchase #6	$98.34	8.610%	$106.8071	$106.81	$106.80	$106.80
Purchase #7	$95.32	5.196%	$100.2728	$100.27	$100.25	$100.30
7 purchase totals =	$754.99		$832.3265	$832.34	$832.30	$832.30