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	$207.94	5.262%	$218.8818	$218.88	$218.90	$218.90
Purchase #2	$128.88	11.655%	$143.901	$143.90	$143.90	$143.90
Purchase #3	$207.28	7.443%	$222.7079	$222.71	$222.70	$222.70
Purchase #4	$192.47	3.855%	$199.8897	$199.89	$199.90	$199.90
Purchase #5	$150.65	11.794%	$168.4177	$168.42	$168.40	$168.40
Purchase #6	$75.48	9.579%	$82.7102	$82.71	$82.70	$82.70
Purchase #7	$208.39	9.507%	$228.2016	$228.20	$228.20	$228.20
7 purchase totals =	$1,171.09		$1,264.7099	$1,264.71	$1,264.70	$1,264.70