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	$151.66	11.208%	$168.6581	$168.66	$168.65	$168.70
Purchase #2	$241.62	9.251%	$263.9723	$263.97	$263.95	$264.00
Purchase #3	$34.34	8.632%	$37.3042	$37.30	$37.30	$37.30
Purchase #4	$182.61	9.711%	$200.3433	$200.34	$200.35	$200.30
Purchase #5	$35.85	13.742%	$40.7765	$40.78	$40.80	$40.80
Purchase #6	$18.81	3.449%	$19.4588	$19.46	$19.45	$19.50
Purchase #7	$181.93	9.636%	$199.4608	$199.46	$199.45	$199.50
7 purchase totals =	$846.82		$929.9740	$929.97	$929.95	$930.10