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	$75.89	7.755%	$81.7753	$81.78	$81.80	$81.80
Purchase #2	$137.61	7.555%	$148.0064	$148.01	$148.00	$148.00
Purchase #3	$142.25	5.687%	$150.3398	$150.34	$150.35	$150.30
Purchase #4	$124.50	11.467%	$138.7764	$138.78	$138.80	$138.80
Purchase #5	$147.93	7.219%	$158.6091	$158.61	$158.60	$158.60
Purchase #6	$227.91	4.497%	$238.1591	$238.16	$238.15	$238.20
Purchase #7	$99.34	4.166%	$103.4785	$103.48	$103.50	$103.50
7 purchase totals =	$955.43		$1,019.1446	$1,019.16	$1,019.20	$1,019.20