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	$63.25	4.353%	$66.0033	$66.00	$66.00	$66.00
Purchase #2	$241.39	13.339%	$273.589	$273.59	$273.60	$273.60
Purchase #3	$190.45	9.841%	$209.1922	$209.19	$209.20	$209.20
Purchase #4	$71.60	9.497%	$78.3999	$78.40	$78.40	$78.40
Purchase #5	$171.84	11.241%	$191.1565	$191.16	$191.15	$191.20
Purchase #6	$6.75	9.503%	$7.3915	$7.39	$7.40	$7.40
Purchase #7	$221.27	6.541%	$235.7433	$235.74	$235.75	$235.70
7 purchase totals =	$966.55		$1,061.4757	$1,061.47	$1,061.50	$1,061.50