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	$166.55	11.343%	$185.4418	$185.44	$185.45	$185.40
Purchase #2	$33.29	5.832%	$35.2315	$35.23	$35.25	$35.20
Purchase #3	$244.70	11.690%	$273.3054	$273.31	$273.30	$273.30
Purchase #4	$45.63	4.269%	$47.5779	$47.58	$47.60	$47.60
Purchase #5	$248.57	12.825%	$280.4491	$280.45	$280.45	$280.40
Purchase #6	$203.78	11.140%	$226.4811	$226.48	$226.50	$226.50
Purchase #7	$189.39	11.525%	$211.2172	$211.22	$211.20	$211.20
7 purchase totals =	$1,131.91		$1,259.7040	$1,259.71	$1,259.75	$1,259.60