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	$213.99	11.756%	$239.1467	$239.15	$239.15	$239.10
Purchase #2	$227.33	10.682%	$251.6134	$251.61	$251.60	$251.60
Purchase #3	$100.60	9.211%	$109.8663	$109.87	$109.85	$109.90
Purchase #4	$203.71	7.141%	$218.2569	$218.26	$218.25	$218.30
Purchase #5	$198.49	5.361%	$209.131	$209.13	$209.15	$209.10
Purchase #6	$68.61	11.625%	$76.5859	$76.59	$76.60	$76.60
Purchase #7	$172.88	13.550%	$196.3052	$196.31	$196.30	$196.30
7 purchase totals =	$1,185.61		$1,300.9054	$1,300.92	$1,300.90	$1,300.90