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	$152.89	8.504%	$165.8918	$165.89	$165.90	$165.90
Purchase #2	$11.98	12.778%	$13.5108	$13.51	$13.50	$13.50
Purchase #3	$116.79	6.342%	$124.1968	$124.20	$124.20	$124.20
Purchase #4	$236.87	4.715%	$248.0384	$248.04	$248.05	$248.00
Purchase #5	$72.89	3.441%	$75.3981	$75.40	$75.40	$75.40
Purchase #6	$175.84	11.845%	$196.6682	$196.67	$196.65	$196.70
Purchase #7	$11.98	12.804%	$13.5139	$13.51	$13.50	$13.50
7 purchase totals =	$779.24		$837.2180	$837.22	$837.20	$837.20