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	$35.26	3.720%	$36.5717	$36.57	$36.55	$36.60
Purchase #2	$51.32	7.179%	$55.0043	$55.00	$55.00	$55.00
Purchase #3	$182.50	7.446%	$196.089	$196.09	$196.10	$196.10
Purchase #4	$146.81	13.644%	$166.8408	$166.84	$166.85	$166.80
Purchase #5	$242.30	8.240%	$262.2655	$262.27	$262.25	$262.30
Purchase #6	$135.59	12.630%	$152.715	$152.72	$152.70	$152.70
Purchase #7	$44.65	4.547%	$46.6802	$46.68	$46.70	$46.70
7 purchase totals =	$838.43		$916.1665	$916.17	$916.15	$916.20