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	$82.63	8.131%	$89.3486	$89.35	$89.35	$89.30
Purchase #2	$213.58	11.455%	$238.0456	$238.05	$238.05	$238.00
Purchase #3	$47.62	12.814%	$53.722	$53.72	$53.70	$53.70
Purchase #4	$169.64	5.268%	$178.5766	$178.58	$178.60	$178.60
Purchase #5	$131.89	8.569%	$143.1917	$143.19	$143.20	$143.20
Purchase #6	$86.79	9.670%	$95.1826	$95.18	$95.20	$95.20
Purchase #7	$148.68	5.277%	$156.5258	$156.53	$156.55	$156.50
7 purchase totals =	$880.83		$954.5929	$954.60	$954.65	$954.50