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	$241.45	10.111%	$265.863	$265.86	$265.85	$265.90
Purchase #2	$118.53	5.114%	$124.5916	$124.59	$124.60	$124.60
Purchase #3	$88.35	8.552%	$95.9057	$95.91	$95.90	$95.90
Purchase #4	$199.78	3.431%	$206.6345	$206.63	$206.65	$206.60
Purchase #5	$31.55	11.844%	$35.2868	$35.29	$35.30	$35.30
Purchase #6	$190.69	9.280%	$208.386	$208.39	$208.40	$208.40
Purchase #7	$217.28	5.805%	$229.8931	$229.89	$229.90	$229.90
7 purchase totals =	$1,087.63		$1,166.5607	$1,166.56	$1,166.60	$1,166.60