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	$30.63	7.513%	$32.9312	$32.93	$32.95	$32.90
Purchase #2	$150.45	10.855%	$166.7813	$166.78	$166.80	$166.80
Purchase #3	$29.72	4.750%	$31.1317	$31.13	$31.15	$31.10
Purchase #4	$218.76	8.342%	$237.009	$237.01	$237.00	$237.00
Purchase #5	$225.33	13.632%	$256.047	$256.05	$256.05	$256.00
Purchase #6	$63.71	12.624%	$71.7528	$71.75	$71.75	$71.80
Purchase #7	$162.69	3.497%	$168.3793	$168.38	$168.40	$168.40
7 purchase totals =	$881.29		$964.0323	$964.03	$964.10	$964.00