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	$178.34	8.615%	$193.704	$193.70	$193.70	$193.70
Purchase #2	$173.31	7.235%	$185.849	$185.85	$185.85	$185.80
Purchase #3	$78.88	8.352%	$85.4681	$85.47	$85.45	$85.50
Purchase #4	$22.38	9.660%	$24.5419	$24.54	$24.55	$24.50
Purchase #5	$30.89	8.560%	$33.5342	$33.53	$33.55	$33.50
Purchase #6	$84.90	6.647%	$90.5433	$90.54	$90.55	$90.50
Purchase #7	$95.29	7.353%	$102.2967	$102.30	$102.30	$102.30
7 purchase totals =	$663.99		$715.9372	$715.93	$715.95	$715.80