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	$191.33	13.809%	$217.7508	$217.75	$217.75	$217.80
Purchase #2	$31.77	9.282%	$34.7189	$34.72	$34.70	$34.70
Purchase #3	$80.75	11.741%	$90.2309	$90.23	$90.25	$90.20
Purchase #4	$130.92	8.115%	$141.5442	$141.54	$141.55	$141.50
Purchase #5	$159.48	4.176%	$166.1399	$166.14	$166.15	$166.10
Purchase #6	$192.96	12.697%	$217.4601	$217.46	$217.45	$217.50
Purchase #7	$163.57	11.105%	$181.7344	$181.73	$181.75	$181.70
7 purchase totals =	$950.78		$1,049.5792	$1,049.57	$1,049.60	$1,049.50