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	$244.90	3.689%	$253.9344	$253.93	$253.95	$253.90
Purchase #2	$102.78	6.715%	$109.6817	$109.68	$109.70	$109.70
Purchase #3	$203.75	3.575%	$211.0341	$211.03	$211.05	$211.00
Purchase #4	$64.30	3.314%	$66.4309	$66.43	$66.45	$66.40
Purchase #5	$35.66	3.782%	$37.0087	$37.01	$37.00	$37.00
Purchase #6	$150.37	3.487%	$155.6134	$155.61	$155.60	$155.60
Purchase #7	$9.76	9.726%	$10.7093	$10.71	$10.70	$10.70
7 purchase totals =	$811.52		$844.4125	$844.40	$844.45	$844.30