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	$73.69	13.412%	$83.5733	$83.57	$83.55	$83.60
Purchase #2	$206.67	4.353%	$215.6663	$215.67	$215.65	$215.70
Purchase #3	$92.93	8.365%	$100.7036	$100.70	$100.70	$100.70
Purchase #4	$235.58	11.746%	$263.2512	$263.25	$263.25	$263.30
Purchase #5	$192.36	3.556%	$199.2003	$199.20	$199.20	$199.20
Purchase #6	$208.90	4.605%	$218.5198	$218.52	$218.50	$218.50
Purchase #7	$14.29	11.103%	$15.8766	$15.88	$15.90	$15.90
7 purchase totals =	$1,024.42		$1,096.7911	$1,096.79	$1,096.75	$1,096.90