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	$204.59	4.862%	$214.5372	$214.54	$214.55	$214.50
Purchase #2	$112.38	6.701%	$119.9106	$119.91	$119.90	$119.90
Purchase #3	$87.90	12.524%	$98.9086	$98.91	$98.90	$98.90
Purchase #4	$42.93	3.444%	$44.4085	$44.41	$44.40	$44.40
Purchase #5	$187.37	9.188%	$204.5856	$204.59	$204.60	$204.60
Purchase #6	$55.46	11.602%	$61.8945	$61.89	$61.90	$61.90
Purchase #7	$231.28	9.517%	$253.2909	$253.29	$253.30	$253.30
7 purchase totals =	$921.91		$997.5359	$997.54	$997.55	$997.50