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	$82.37	13.257%	$93.2898	$93.29	$93.30	$93.30
Purchase #2	$132.89	6.762%	$141.876	$141.88	$141.90	$141.90
Purchase #3	$222.75	6.160%	$236.4714	$236.47	$236.45	$236.50
Purchase #4	$207.89	11.804%	$232.4293	$232.43	$232.45	$232.40
Purchase #5	$75.27	13.264%	$85.2538	$85.25	$85.25	$85.30
Purchase #6	$182.79	5.476%	$192.7996	$192.80	$192.80	$192.80
Purchase #7	$100.55	10.841%	$111.4506	$111.45	$111.45	$111.50
7 purchase totals =	$1,004.51		$1,093.5705	$1,093.57	$1,093.60	$1,093.70