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	$34.43	5.506%	$36.3257	$36.33	$36.35	$36.30
Purchase #2	$59.86	9.375%	$65.4719	$65.47	$65.45	$65.50
Purchase #3	$116.88	8.426%	$126.7283	$126.73	$126.75	$126.70
Purchase #4	$154.89	12.104%	$173.6379	$173.64	$173.65	$173.60
Purchase #5	$221.98	13.522%	$251.9961	$252.00	$252.00	$252.00
Purchase #6	$182.59	3.220%	$188.4694	$188.47	$188.45	$188.50
Purchase #7	$183.93	3.449%	$190.2737	$190.27	$190.25	$190.30
7 purchase totals =	$954.56		$1,032.9030	$1,032.91	$1,032.90	$1,032.90