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	$112.42	9.448%	$123.0414	$123.04	$123.05	$123.00
Purchase #2	$72.71	13.866%	$82.792	$82.79	$82.80	$82.80
Purchase #3	$95.69	8.119%	$103.4591	$103.46	$103.45	$103.50
Purchase #4	$117.25	10.180%	$129.1861	$129.19	$129.20	$129.20
Purchase #5	$244.95	3.702%	$254.018	$254.02	$254.00	$254.00
Purchase #6	$167.89	6.772%	$179.2595	$179.26	$179.25	$179.30
Purchase #7	$20.85	12.857%	$23.5307	$23.53	$23.55	$23.50
7 purchase totals =	$831.76		$895.2868	$895.29	$895.30	$895.30