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	$209.51	13.837%	$238.4999	$238.50	$238.50	$238.50
Purchase #2	$21.75	3.507%	$22.5128	$22.51	$22.50	$22.50
Purchase #3	$51.38	8.823%	$55.9133	$55.91	$55.90	$55.90
Purchase #4	$249.25	12.581%	$280.6081	$280.61	$280.60	$280.60
Purchase #5	$222.31	6.365%	$236.46	$236.46	$236.45	$236.50
Purchase #6	$34.76	3.371%	$35.9318	$35.93	$35.95	$35.90
Purchase #7	$58.86	9.494%	$64.4482	$64.45	$64.45	$64.40
7 purchase totals =	$847.82		$934.3741	$934.37	$934.35	$934.30