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	$113.35	4.245%	$118.1617	$118.16	$118.15	$118.20
Purchase #2	$11.45	12.749%	$12.9098	$12.91	$12.90	$12.90
Purchase #3	$242.68	13.687%	$275.8956	$275.90	$275.90	$275.90
Purchase #4	$100.62	9.113%	$109.7895	$109.79	$109.80	$109.80
Purchase #5	$106.56	10.559%	$117.8117	$117.81	$117.80	$117.80
Purchase #6	$246.57	5.800%	$260.8711	$260.87	$260.85	$260.90
Purchase #7	$37.37	3.632%	$38.7273	$38.73	$38.75	$38.70
7 purchase totals =	$858.60		$934.1667	$934.17	$934.15	$934.20