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	$130.43	11.373%	$145.2638	$145.26	$145.25	$145.30
Purchase #2	$85.94	10.663%	$95.1038	$95.10	$95.10	$95.10
Purchase #3	$124.52	5.164%	$130.9502	$130.95	$130.95	$131.00
Purchase #4	$57.93	7.241%	$62.1247	$62.12	$62.10	$62.10
Purchase #5	$183.38	13.682%	$208.4701	$208.47	$208.45	$208.50
Purchase #6	$85.89	8.857%	$93.4973	$93.50	$93.50	$93.50
Purchase #7	$148.54	11.468%	$165.5746	$165.57	$165.55	$165.60
7 purchase totals =	$816.63		$900.9845	$900.97	$900.90	$901.10