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	13.290%	$171.8156	$171.82	$171.80	$171.80
Purchase #2	$116.45	10.684%	$128.8915	$128.89	$128.90	$128.90
Purchase #3	$29.84	6.451%	$31.765	$31.77	$31.75	$31.80
Purchase #4	$27.88	13.315%	$31.5922	$31.59	$31.60	$31.60
Purchase #5	$20.95	7.325%	$22.4846	$22.48	$22.50	$22.50
Purchase #6	$229.39	11.777%	$256.4053	$256.41	$256.40	$256.40
Purchase #7	$53.72	12.617%	$60.4979	$60.50	$60.50	$60.50
7 purchase totals =	$629.89		$703.4521	$703.46	$703.45	$703.50