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	$122.83	9.227%	$134.1635	$134.16	$134.15	$134.20
Purchase #2	$206.86	4.228%	$215.606	$215.61	$215.60	$215.60
Purchase #3	$171.87	11.735%	$192.0389	$192.04	$192.05	$192.00
Purchase #4	$238.94	10.662%	$264.4158	$264.42	$264.40	$264.40
Purchase #5	$61.43	9.741%	$67.4139	$67.41	$67.40	$67.40
Purchase #6	$151.89	7.185%	$162.8033	$162.80	$162.80	$162.80
Purchase #7	$40.54	11.382%	$45.1543	$45.15	$45.15	$45.20
7 purchase totals =	$994.36		$1,081.5957	$1,081.59	$1,081.55	$1,081.60