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	$222.85	8.532%	$241.8636	$241.86	$241.85	$241.90
Purchase #2	$43.91	5.787%	$46.4511	$46.45	$46.45	$46.50
Purchase #3	$130.99	10.153%	$144.2894	$144.29	$144.30	$144.30
Purchase #4	$7.42	6.203%	$7.8803	$7.88	$7.90	$7.90
Purchase #5	$44.77	3.829%	$46.4842	$46.48	$46.50	$46.50
Purchase #6	$145.80	3.417%	$150.782	$150.78	$150.80	$150.80
Purchase #7	$112.73	13.714%	$128.1898	$128.19	$128.20	$128.20
7 purchase totals =	$708.47		$765.9404	$765.93	$766.00	$766.10