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	$208.81	11.472%	$232.7647	$232.76	$232.75	$232.80
Purchase #2	$180.82	9.786%	$198.515	$198.52	$198.50	$198.50
Purchase #3	$123.62	3.346%	$127.7563	$127.76	$127.75	$127.80
Purchase #4	$33.85	6.210%	$35.9521	$35.95	$35.95	$36.00
Purchase #5	$142.42	6.593%	$151.8098	$151.81	$151.80	$151.80
Purchase #6	$83.64	9.460%	$91.5523	$91.55	$91.55	$91.60
Purchase #7	$111.52	4.575%	$116.622	$116.62	$116.60	$116.60
7 purchase totals =	$884.68		$954.9722	$954.97	$954.90	$955.10