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	$97.27	4.320%	$101.4721	$101.47	$101.45	$101.50
Purchase #2	$130.45	11.205%	$145.0669	$145.07	$145.05	$145.10
Purchase #3	$85.73	5.429%	$90.3843	$90.38	$90.40	$90.40
Purchase #4	$86.67	7.212%	$92.9206	$92.92	$92.90	$92.90
Purchase #5	$184.49	12.765%	$208.0401	$208.04	$208.05	$208.00
Purchase #6	$40.45	5.246%	$42.572	$42.57	$42.55	$42.60
Purchase #7	$125.32	6.588%	$133.5761	$133.58	$133.60	$133.60
7 purchase totals =	$750.38		$814.0321	$814.03	$814.00	$814.10