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	$37.81	7.766%	$40.7463	$40.75	$40.75	$40.70
Purchase #2	$22.74	5.394%	$23.9666	$23.97	$23.95	$24.00
Purchase #3	$34.50	10.786%	$38.2212	$38.22	$38.20	$38.20
Purchase #4	$213.79	5.415%	$225.3667	$225.37	$225.35	$225.40
Purchase #5	$57.78	3.497%	$59.8006	$59.80	$59.80	$59.80
Purchase #6	$250.46	11.308%	$278.782	$278.78	$278.80	$278.80
Purchase #7	$33.85	5.288%	$35.64	$35.64	$35.65	$35.60
7 purchase totals =	$650.93		$702.5234	$702.53	$702.50	$702.50