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	$152.67	11.695%	$170.5248	$170.52	$170.50	$170.50
Purchase #2	$196.75	13.748%	$223.7992	$223.80	$223.80	$223.80
Purchase #3	$46.80	12.421%	$52.613	$52.61	$52.60	$52.60
Purchase #4	$248.54	8.789%	$270.3842	$270.38	$270.40	$270.40
Purchase #5	$146.80	7.290%	$157.5017	$157.50	$157.50	$157.50
Purchase #6	$77.34	11.807%	$86.4715	$86.47	$86.45	$86.50
Purchase #7	$44.48	12.439%	$50.0129	$50.01	$50.00	$50.00
7 purchase totals =	$913.38		$1,011.3073	$1,011.29	$1,011.25	$1,011.30