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	$131.99	12.709%	$148.7646	$148.76	$148.75	$148.80
Purchase #2	$132.94	5.772%	$140.6133	$140.61	$140.60	$140.60
Purchase #3	$45.80	13.338%	$51.9088	$51.91	$51.90	$51.90
Purchase #4	$34.32	7.636%	$36.9407	$36.94	$36.95	$36.90
Purchase #5	$188.27	6.477%	$200.4642	$200.46	$200.45	$200.50
Purchase #6	$213.91	7.764%	$230.518	$230.52	$230.50	$230.50
Purchase #7	$81.37	6.248%	$86.454	$86.45	$86.45	$86.50
7 purchase totals =	$828.60		$895.6636	$895.65	$895.60	$895.70