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	$111.90	10.542%	$123.6965	$123.70	$123.70	$123.70
Purchase #2	$35.93	4.566%	$37.5706	$37.57	$37.55	$37.60
Purchase #3	$48.83	6.508%	$52.0079	$52.01	$52.00	$52.00
Purchase #4	$228.32	8.568%	$247.8825	$247.88	$247.90	$247.90
Purchase #5	$166.47	9.799%	$182.7824	$182.78	$182.80	$182.80
Purchase #6	$54.51	11.171%	$60.5993	$60.60	$60.60	$60.60
Purchase #7	$83.45	10.321%	$92.0629	$92.06	$92.05	$92.10
7 purchase totals =	$729.41		$796.6021	$796.60	$796.60	$796.70