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	$155.70	5.739%	$164.6356	$164.64	$164.65	$164.60
Purchase #2	$239.36	11.377%	$266.592	$266.59	$266.60	$266.60
Purchase #3	$63.79	13.170%	$72.1911	$72.19	$72.20	$72.20
Purchase #4	$75.89	9.851%	$83.3659	$83.37	$83.35	$83.40
Purchase #5	$218.87	3.665%	$226.8916	$226.89	$226.90	$226.90
Purchase #6	$31.87	12.753%	$35.9344	$35.93	$35.95	$35.90
Purchase #7	$144.85	8.675%	$157.4157	$157.42	$157.40	$157.40
7 purchase totals =	$930.33		$1,007.0263	$1,007.03	$1,007.05	$1,007.00