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	$243.54	4.756%	$255.1228	$255.12	$255.10	$255.10
Purchase #2	$9.28	12.527%	$10.4425	$10.44	$10.45	$10.40
Purchase #3	$38.29	10.153%	$42.1776	$42.18	$42.20	$42.20
Purchase #4	$110.50	12.143%	$123.918	$123.92	$123.90	$123.90
Purchase #5	$164.75	11.784%	$184.1641	$184.16	$184.15	$184.20
Purchase #6	$9.35	12.265%	$10.4968	$10.50	$10.50	$10.50
Purchase #7	$35.44	13.405%	$40.1907	$40.19	$40.20	$40.20
7 purchase totals =	$611.15		$666.5125	$666.51	$666.50	$666.50