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	$76.55	11.590%	$85.4221	$85.42	$85.40	$85.40
Purchase #2	$231.32	8.189%	$250.2628	$250.26	$250.25	$250.30
Purchase #3	$131.72	6.745%	$140.6045	$140.60	$140.60	$140.60
Purchase #4	$177.29	10.121%	$195.2335	$195.23	$195.25	$195.20
Purchase #5	$232.98	10.483%	$257.4033	$257.40	$257.40	$257.40
Purchase #6	$106.80	4.597%	$111.7096	$111.71	$111.70	$111.70
Purchase #7	$72.92	4.686%	$76.337	$76.34	$76.35	$76.30
7 purchase totals =	$1,029.58		$1,116.9728	$1,116.96	$1,116.95	$1,116.90