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	$42.47	8.142%	$45.9279	$45.93	$45.95	$45.90
Purchase #2	$208.44	11.197%	$231.779	$231.78	$231.80	$231.80
Purchase #3	$87.44	3.106%	$90.1559	$90.16	$90.15	$90.20
Purchase #4	$27.61	9.169%	$30.1416	$30.14	$30.15	$30.10
Purchase #5	$219.46	13.166%	$248.3541	$248.35	$248.35	$248.40
Purchase #6	$228.35	3.741%	$236.8926	$236.89	$236.90	$236.90
Purchase #7	$201.65	13.847%	$229.5725	$229.57	$229.55	$229.60
7 purchase totals =	$1,015.42		$1,112.8236	$1,112.82	$1,112.85	$1,112.90