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	$168.38	4.491%	$175.9419	$175.94	$175.95	$175.90
Purchase #2	$140.39	8.800%	$152.7443	$152.74	$152.75	$152.70
Purchase #3	$134.65	3.781%	$139.7411	$139.74	$139.75	$139.70
Purchase #4	$90.74	10.314%	$100.0989	$100.10	$100.10	$100.10
Purchase #5	$109.34	7.402%	$117.4333	$117.43	$117.45	$117.40
Purchase #6	$64.28	7.358%	$69.0097	$69.01	$69.00	$69.00
Purchase #7	$30.39	13.571%	$34.5142	$34.51	$34.50	$34.50
7 purchase totals =	$738.17		$789.4834	$789.47	$789.50	$789.30