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	$247.42	12.244%	$277.7141	$277.71	$277.70	$277.70
Purchase #2	$35.37	11.484%	$39.4319	$39.43	$39.45	$39.40
Purchase #3	$31.46	6.840%	$33.6119	$33.61	$33.60	$33.60
Purchase #4	$212.82	12.141%	$238.6585	$238.66	$238.65	$238.70
Purchase #5	$100.37	3.870%	$104.2543	$104.25	$104.25	$104.30
Purchase #6	$176.67	7.533%	$189.9786	$189.98	$190.00	$190.00
Purchase #7	$142.90	6.561%	$152.2757	$152.28	$152.30	$152.30
7 purchase totals =	$947.01		$1,035.9250	$1,035.92	$1,035.95	$1,036.00