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	$211.44	12.627%	$238.1385	$238.14	$238.15	$238.10
Purchase #2	$78.43	6.301%	$83.3719	$83.37	$83.35	$83.40
Purchase #3	$175.88	5.677%	$185.8647	$185.86	$185.85	$185.90
Purchase #4	$214.48	11.715%	$239.6063	$239.61	$239.60	$239.60
Purchase #5	$144.68	6.605%	$154.2361	$154.24	$154.25	$154.20
Purchase #6	$125.44	5.526%	$132.3718	$132.37	$132.35	$132.40
Purchase #7	$71.42	8.330%	$77.3693	$77.37	$77.35	$77.40
7 purchase totals =	$1,021.77		$1,110.9586	$1,110.96	$1,110.90	$1,111.00