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	$179.94	6.111%	$190.9361	$190.94	$190.95	$190.90
Purchase #2	$184.77	5.485%	$194.9046	$194.90	$194.90	$194.90
Purchase #3	$165.39	13.509%	$187.7325	$187.73	$187.75	$187.70
Purchase #4	$70.43	11.490%	$78.5224	$78.52	$78.50	$78.50
Purchase #5	$188.86	11.748%	$211.0473	$211.05	$211.05	$211.00
Purchase #6	$123.50	13.390%	$140.0367	$140.04	$140.05	$140.00
Purchase #7	$242.82	7.612%	$261.3035	$261.30	$261.30	$261.30
7 purchase totals =	$1,155.71		$1,264.4831	$1,264.48	$1,264.50	$1,264.30