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	$215.88	3.579%	$223.6063	$223.61	$223.60	$223.60
Purchase #2	$97.59	3.163%	$100.6768	$100.68	$100.70	$100.70
Purchase #3	$241.92	10.282%	$266.7942	$266.79	$266.80	$266.80
Purchase #4	$112.60	6.464%	$119.8785	$119.88	$119.90	$119.90
Purchase #5	$26.48	8.462%	$28.7207	$28.72	$28.70	$28.70
Purchase #6	$27.85	3.730%	$28.8888	$28.89	$28.90	$28.90
Purchase #7	$69.78	12.695%	$78.6386	$78.64	$78.65	$78.60
7 purchase totals =	$792.10		$847.2039	$847.21	$847.25	$847.20