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	$35.43	7.742%	$38.173	$38.17	$38.15	$38.20
Purchase #2	$29.51	5.650%	$31.1773	$31.18	$31.20	$31.20
Purchase #3	$131.66	4.188%	$137.1739	$137.17	$137.15	$137.20
Purchase #4	$214.68	10.730%	$237.7152	$237.72	$237.70	$237.70
Purchase #5	$99.95	12.432%	$112.3758	$112.38	$112.40	$112.40
Purchase #6	$242.43	5.103%	$254.8012	$254.80	$254.80	$254.80
Purchase #7	$38.78	4.327%	$40.458	$40.46	$40.45	$40.50
7 purchase totals =	$792.44		$851.8744	$851.88	$851.85	$852.00