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	$37.37	3.147%	$38.546	$38.55	$38.55	$38.50
Purchase #2	$63.31	12.741%	$71.3763	$71.38	$71.40	$71.40
Purchase #3	$214.72	13.634%	$243.9949	$243.99	$244.00	$244.00
Purchase #4	$197.55	12.233%	$221.7163	$221.72	$221.70	$221.70
Purchase #5	$73.97	5.502%	$78.0398	$78.04	$78.05	$78.00
Purchase #6	$144.84	6.425%	$154.146	$154.15	$154.15	$154.10
Purchase #7	$33.28	6.606%	$35.4785	$35.48	$35.50	$35.50
7 purchase totals =	$765.04		$843.2978	$843.31	$843.35	$843.20