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	$205.86	9.558%	$225.5361	$225.54	$225.55	$225.50
Purchase #2	$78.97	8.246%	$85.4819	$85.48	$85.50	$85.50
Purchase #3	$29.33	7.246%	$31.4553	$31.46	$31.45	$31.50
Purchase #4	$62.88	13.672%	$71.477	$71.48	$71.50	$71.50
Purchase #5	$146.78	8.185%	$158.7939	$158.79	$158.80	$158.80
Purchase #6	$157.89	6.326%	$167.8781	$167.88	$167.90	$167.90
Purchase #7	$86.29	12.646%	$97.2022	$97.20	$97.20	$97.20
7 purchase totals =	$768.00		$837.8245	$837.83	$837.90	$837.90