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	$185.37	3.806%	$192.4252	$192.43	$192.45	$192.40
Purchase #2	$94.61	11.184%	$105.1912	$105.19	$105.20	$105.20
Purchase #3	$135.54	4.681%	$141.8846	$141.88	$141.90	$141.90
Purchase #4	$169.50	6.792%	$181.0124	$181.01	$181.00	$181.00
Purchase #5	$146.83	7.425%	$157.7321	$157.73	$157.75	$157.70
Purchase #6	$83.36	7.707%	$89.7846	$89.78	$89.80	$89.80
Purchase #7	$176.85	12.695%	$199.3011	$199.30	$199.30	$199.30
7 purchase totals =	$992.06		$1,067.3312	$1,067.32	$1,067.40	$1,067.30