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	$127.85	12.498%	$143.8287	$143.83	$143.85	$143.80
Purchase #2	$182.82	5.342%	$192.5862	$192.59	$192.60	$192.60
Purchase #3	$225.51	3.464%	$233.3217	$233.32	$233.30	$233.30
Purchase #4	$178.27	7.430%	$191.5155	$191.52	$191.50	$191.50
Purchase #5	$10.51	11.276%	$11.6951	$11.70	$11.70	$11.70
Purchase #6	$131.37	6.182%	$139.4913	$139.49	$139.50	$139.50
Purchase #7	$227.96	7.624%	$245.3397	$245.34	$245.35	$245.30
7 purchase totals =	$1,084.29		$1,157.7782	$1,157.79	$1,157.80	$1,157.70