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	$31.33	5.369%	$33.0121	$33.01	$33.00	$33.00
Purchase #2	$67.87	12.757%	$76.5282	$76.53	$76.55	$76.50
Purchase #3	$102.26	9.555%	$112.0309	$112.03	$112.05	$112.00
Purchase #4	$151.42	3.330%	$156.4623	$156.46	$156.45	$156.50
Purchase #5	$30.28	4.816%	$31.7383	$31.74	$31.75	$31.70
Purchase #6	$227.29	4.634%	$237.8226	$237.82	$237.80	$237.80
Purchase #7	$100.87	11.594%	$112.5649	$112.56	$112.55	$112.60
7 purchase totals =	$711.32		$760.1593	$760.15	$760.15	$760.10