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	$13.56	3.693%	$14.0608	$14.06	$14.05	$14.10
Purchase #2	$217.59	6.193%	$231.0653	$231.07	$231.05	$231.10
Purchase #3	$220.81	10.223%	$243.3834	$243.38	$243.40	$243.40
Purchase #4	$234.74	6.518%	$250.0404	$250.04	$250.05	$250.00
Purchase #5	$6.95	8.169%	$7.5177	$7.52	$7.50	$7.50
Purchase #6	$76.95	11.652%	$85.9162	$85.92	$85.90	$85.90
Purchase #7	$96.89	13.129%	$109.6107	$109.61	$109.60	$109.60
7 purchase totals =	$867.49		$941.5945	$941.60	$941.55	$941.60