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	$37.89	13.618%	$43.0499	$43.05	$43.05	$43.00
Purchase #2	$40.51	7.622%	$43.5977	$43.60	$43.60	$43.60
Purchase #3	$71.33	13.120%	$80.6885	$80.69	$80.70	$80.70
Purchase #4	$96.84	10.127%	$106.647	$106.65	$106.65	$106.60
Purchase #5	$30.39	7.528%	$32.6778	$32.68	$32.70	$32.70
Purchase #6	$135.33	3.141%	$139.5807	$139.58	$139.60	$139.60
Purchase #7	$226.89	4.762%	$237.6945	$237.69	$237.70	$237.70
7 purchase totals =	$639.18		$683.9361	$683.94	$684.00	$683.90