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	$176.42	7.827%	$190.2284	$190.23	$190.25	$190.20
Purchase #2	$106.73	10.686%	$118.1352	$118.14	$118.15	$118.10
Purchase #3	$243.67	13.222%	$275.888	$275.89	$275.90	$275.90
Purchase #4	$165.83	4.484%	$173.2658	$173.27	$173.25	$173.30
Purchase #5	$77.53	9.289%	$84.7318	$84.73	$84.75	$84.70
Purchase #6	$126.50	10.775%	$140.1304	$140.13	$140.15	$140.10
Purchase #7	$52.59	9.295%	$57.4782	$57.48	$57.50	$57.50
7 purchase totals =	$949.27		$1,039.8578	$1,039.87	$1,039.95	$1,039.80