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	$53.52	13.410%	$60.697	$60.70	$60.70	$60.70
Purchase #2	$246.37	10.820%	$273.0272	$273.03	$273.05	$273.00
Purchase #3	$99.82	3.811%	$103.6241	$103.62	$103.60	$103.60
Purchase #4	$97.29	3.547%	$100.7409	$100.74	$100.75	$100.70
Purchase #5	$179.90	4.321%	$187.6735	$187.67	$187.65	$187.70
Purchase #6	$182.54	9.829%	$200.4819	$200.48	$200.50	$200.50
Purchase #7	$38.86	3.554%	$40.2411	$40.24	$40.25	$40.20
7 purchase totals =	$898.30		$966.4857	$966.48	$966.50	$966.40