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	$104.43	7.130%	$111.8759	$111.88	$111.90	$111.90
Purchase #2	$184.99	13.732%	$210.3928	$210.39	$210.40	$210.40
Purchase #3	$168.43	12.276%	$189.1065	$189.11	$189.10	$189.10
Purchase #4	$139.56	3.682%	$144.6986	$144.70	$144.70	$144.70
Purchase #5	$115.58	9.509%	$126.5705	$126.57	$126.55	$126.60
Purchase #6	$140.31	13.522%	$159.2827	$159.28	$159.30	$159.30
Purchase #7	$41.64	4.490%	$43.5096	$43.51	$43.50	$43.50
7 purchase totals =	$894.94		$985.4366	$985.44	$985.45	$985.50