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	$117.37	12.134%	$131.6117	$131.61	$131.60	$131.60
Purchase #2	$14.67	5.428%	$15.4663	$15.47	$15.45	$15.50
Purchase #3	$219.61	8.709%	$238.7358	$238.74	$238.75	$238.70
Purchase #4	$159.67	5.591%	$168.5971	$168.60	$168.60	$168.60
Purchase #5	$74.48	10.805%	$82.5276	$82.53	$82.55	$82.50
Purchase #6	$177.99	6.611%	$189.7569	$189.76	$189.75	$189.80
Purchase #7	$217.63	9.324%	$237.9218	$237.92	$237.90	$237.90
7 purchase totals =	$981.42		$1,064.6172	$1,064.63	$1,064.60	$1,064.60