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	$187.88	6.699%	$200.4661	$200.47	$200.45	$200.50
Purchase #2	$210.54	3.631%	$218.1847	$218.18	$218.20	$218.20
Purchase #3	$66.34	8.771%	$72.1587	$72.16	$72.15	$72.20
Purchase #4	$52.88	6.610%	$56.3754	$56.38	$56.40	$56.40
Purchase #5	$232.83	11.653%	$259.9617	$259.96	$259.95	$260.00
Purchase #6	$13.45	12.718%	$15.1606	$15.16	$15.15	$15.20
Purchase #7	$28.98	7.594%	$31.1807	$31.18	$31.20	$31.20
7 purchase totals =	$792.90		$853.4879	$853.49	$853.50	$853.70