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	$84.91	4.165%	$88.4465	$88.45	$88.45	$88.40
Purchase #2	$243.58	8.179%	$263.5024	$263.50	$263.50	$263.50
Purchase #3	$70.85	10.674%	$78.4125	$78.41	$78.40	$78.40
Purchase #4	$43.57	11.685%	$48.6612	$48.66	$48.65	$48.70
Purchase #5	$200.54	4.141%	$208.8444	$208.84	$208.85	$208.80
Purchase #6	$125.80	9.560%	$137.8265	$137.83	$137.85	$137.80
Purchase #7	$50.96	9.194%	$55.6453	$55.65	$55.65	$55.60
7 purchase totals =	$820.21		$881.3388	$881.34	$881.35	$881.20