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	$55.76	9.737%	$61.1894	$61.19	$61.20	$61.20
Purchase #2	$150.43	3.139%	$155.152	$155.15	$155.15	$155.20
Purchase #3	$114.79	10.218%	$126.5192	$126.52	$126.50	$126.50
Purchase #4	$101.49	7.696%	$109.3007	$109.30	$109.30	$109.30
Purchase #5	$126.58	4.551%	$132.3407	$132.34	$132.35	$132.30
Purchase #6	$249.90	9.221%	$272.9433	$272.94	$272.95	$272.90
Purchase #7	$126.29	11.665%	$141.0217	$141.02	$141.00	$141.00
7 purchase totals =	$925.24		$998.4670	$998.46	$998.45	$998.40