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	$119.28	5.831%	$126.2352	$126.24	$126.25	$126.20
Purchase #2	$95.56	5.345%	$100.6677	$100.67	$100.65	$100.70
Purchase #3	$126.51	10.640%	$139.9707	$139.97	$139.95	$140.00
Purchase #4	$8.50	4.326%	$8.8677	$8.87	$8.85	$8.90
Purchase #5	$77.33	7.804%	$83.3648	$83.36	$83.35	$83.40
Purchase #6	$74.94	10.340%	$82.6888	$82.69	$82.70	$82.70
Purchase #7	$165.78	8.271%	$179.4917	$179.49	$179.50	$179.50
7 purchase totals =	$667.90		$721.2866	$721.29	$721.25	$721.40