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	$106.57	11.818%	$119.1644	$119.16	$119.15	$119.20
Purchase #2	$219.49	11.552%	$244.8455	$244.85	$244.85	$244.80
Purchase #3	$29.90	8.840%	$32.5432	$32.54	$32.55	$32.50
Purchase #4	$140.37	3.251%	$144.9334	$144.93	$144.95	$144.90
Purchase #5	$177.62	10.788%	$196.7816	$196.78	$196.80	$196.80
Purchase #6	$143.81	7.418%	$154.4778	$154.48	$154.50	$154.50
Purchase #7	$58.71	6.635%	$62.6054	$62.61	$62.60	$62.60
7 purchase totals =	$876.47		$955.3513	$955.35	$955.40	$955.30