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	$142.61	13.644%	$162.0677	$162.07	$162.05	$162.10
Purchase #2	$75.89	10.158%	$83.5989	$83.60	$83.60	$83.60
Purchase #3	$207.40	9.486%	$227.074	$227.07	$227.05	$227.10
Purchase #4	$156.53	13.722%	$178.009	$178.01	$178.00	$178.00
Purchase #5	$155.33	8.703%	$168.8484	$168.85	$168.85	$168.80
Purchase #6	$187.60	10.574%	$207.4368	$207.44	$207.45	$207.40
Purchase #7	$92.94	3.429%	$96.1269	$96.13	$96.15	$96.10
7 purchase totals =	$1,018.30		$1,123.1617	$1,123.17	$1,123.15	$1,123.10