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	$83.72	7.671%	$90.1422	$90.14	$90.15	$90.10
Purchase #2	$108.47	13.490%	$123.1026	$123.10	$123.10	$123.10
Purchase #3	$33.47	7.130%	$35.8564	$35.86	$35.85	$35.90
Purchase #4	$140.67	5.669%	$148.6446	$148.64	$148.65	$148.60
Purchase #5	$212.93	13.560%	$241.8033	$241.80	$241.80	$241.80
Purchase #6	$37.53	8.430%	$40.6938	$40.69	$40.70	$40.70
Purchase #7	$161.78	12.643%	$182.2338	$182.23	$182.25	$182.20
7 purchase totals =	$778.57		$862.4767	$862.46	$862.50	$862.40