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	$98.66	5.797%	$104.3793	$104.38	$104.40	$104.40
Purchase #2	$17.96	11.724%	$20.0656	$20.07	$20.05	$20.10
Purchase #3	$41.29	9.672%	$45.2836	$45.28	$45.30	$45.30
Purchase #4	$171.69	10.703%	$190.066	$190.07	$190.05	$190.10
Purchase #5	$222.58	13.168%	$251.8893	$251.89	$251.90	$251.90
Purchase #6	$188.78	13.358%	$213.9972	$214.00	$214.00	$214.00
Purchase #7	$216.98	6.725%	$231.5719	$231.57	$231.55	$231.60
7 purchase totals =	$957.94		$1,057.2529	$1,057.26	$1,057.25	$1,057.40