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	$40.80	10.643%	$45.1423	$45.14	$45.15	$45.10
Purchase #2	$92.61	3.134%	$95.5124	$95.51	$95.50	$95.50
Purchase #3	$200.89	10.403%	$221.7886	$221.79	$221.80	$221.80
Purchase #4	$62.48	6.214%	$66.3625	$66.36	$66.35	$66.40
Purchase #5	$152.46	12.646%	$171.7401	$171.74	$171.75	$171.70
Purchase #6	$79.34	13.465%	$90.0231	$90.02	$90.00	$90.00
Purchase #7	$241.68	9.446%	$264.5091	$264.51	$264.50	$264.50
7 purchase totals =	$870.26		$955.0781	$955.07	$955.05	$955.00