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	$248.37	8.532%	$269.5609	$269.56	$269.55	$269.60
Purchase #2	$140.40	7.171%	$150.4681	$150.47	$150.45	$150.50
Purchase #3	$210.82	13.517%	$239.3165	$239.32	$239.30	$239.30
Purchase #4	$83.27	7.382%	$89.417	$89.42	$89.40	$89.40
Purchase #5	$200.28	5.125%	$210.5444	$210.54	$210.55	$210.50
Purchase #6	$84.66	10.410%	$93.4731	$93.47	$93.45	$93.50
Purchase #7	$37.82	11.672%	$42.2344	$42.23	$42.25	$42.20
7 purchase totals =	$1,005.62		$1,095.0144	$1,095.01	$1,094.95	$1,095.00