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	$214.81	13.540%	$243.8953	$243.90	$243.90	$243.90
Purchase #2	$157.50	4.315%	$164.2961	$164.30	$164.30	$164.30
Purchase #3	$123.64	3.236%	$127.641	$127.64	$127.65	$127.60
Purchase #4	$74.53	11.604%	$83.1785	$83.18	$83.20	$83.20
Purchase #5	$95.72	8.578%	$103.9309	$103.93	$103.95	$103.90
Purchase #6	$8.90	13.203%	$10.0751	$10.08	$10.10	$10.10
Purchase #7	$188.85	13.230%	$213.8349	$213.83	$213.85	$213.80
7 purchase totals =	$863.95		$946.8518	$946.86	$946.95	$946.80