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	$67.49	9.477%	$73.886	$73.89	$73.90	$73.90
Purchase #2	$37.89	4.738%	$39.6852	$39.69	$39.70	$39.70
Purchase #3	$83.86	9.330%	$91.6841	$91.68	$91.70	$91.70
Purchase #4	$241.77	13.261%	$273.8311	$273.83	$273.85	$273.80
Purchase #5	$235.78	13.623%	$267.9003	$267.90	$267.90	$267.90
Purchase #6	$86.92	8.738%	$94.5151	$94.52	$94.50	$94.50
Purchase #7	$51.93	9.840%	$57.0399	$57.04	$57.05	$57.00
7 purchase totals =	$805.64		$898.5417	$898.55	$898.60	$898.50