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	$67.65	9.194%	$73.8697	$73.87	$73.85	$73.90
Purchase #2	$195.50	6.732%	$208.6611	$208.66	$208.65	$208.70
Purchase #3	$84.50	8.704%	$91.8549	$91.85	$91.85	$91.90
Purchase #4	$214.71	3.288%	$221.7697	$221.77	$221.75	$221.80
Purchase #5	$151.33	11.415%	$168.6043	$168.60	$168.60	$168.60
Purchase #6	$100.50	13.206%	$113.772	$113.77	$113.75	$113.80
Purchase #7	$146.46	12.149%	$164.2534	$164.25	$164.25	$164.30
7 purchase totals =	$960.65		$1,042.7851	$1,042.77	$1,042.70	$1,043.00