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	$141.44	4.699%	$148.0863	$148.09	$148.10	$148.10
Purchase #2	$162.56	4.249%	$169.4672	$169.47	$169.45	$169.50
Purchase #3	$246.83	13.484%	$280.1126	$280.11	$280.10	$280.10
Purchase #4	$250.76	11.476%	$279.5372	$279.54	$279.55	$279.50
Purchase #5	$81.43	7.588%	$87.6089	$87.61	$87.60	$87.60
Purchase #6	$31.61	12.295%	$35.4964	$35.50	$35.50	$35.50
Purchase #7	$199.74	4.514%	$208.7563	$208.76	$208.75	$208.80
7 purchase totals =	$1,114.37		$1,209.0649	$1,209.08	$1,209.05	$1,209.10