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	$56.78	7.287%	$60.9176	$60.92	$60.90	$60.90
Purchase #2	$49.38	6.724%	$52.7003	$52.70	$52.70	$52.70
Purchase #3	$233.60	13.609%	$265.3906	$265.39	$265.40	$265.40
Purchase #4	$141.63	9.770%	$155.4673	$155.47	$155.45	$155.50
Purchase #5	$36.65	3.315%	$37.8649	$37.86	$37.85	$37.90
Purchase #6	$40.53	8.400%	$43.9345	$43.93	$43.95	$43.90
Purchase #7	$121.94	12.392%	$137.0508	$137.05	$137.05	$137.10
7 purchase totals =	$680.51		$753.3260	$753.32	$753.30	$753.40