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	$219.96	9.811%	$241.5403	$241.54	$241.55	$241.50
Purchase #2	$203.42	7.193%	$218.052	$218.05	$218.05	$218.10
Purchase #3	$31.48	4.294%	$32.8318	$32.83	$32.85	$32.80
Purchase #4	$35.99	4.542%	$37.6247	$37.62	$37.60	$37.60
Purchase #5	$242.75	9.130%	$264.9131	$264.91	$264.90	$264.90
Purchase #6	$74.35	8.260%	$80.4913	$80.49	$80.50	$80.50
Purchase #7	$70.37	8.111%	$76.0777	$76.08	$76.10	$76.10
7 purchase totals =	$878.32		$951.5309	$951.52	$951.55	$951.50