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	$189.74	7.762%	$204.4676	$204.47	$204.45	$204.50
Purchase #2	$38.56	5.762%	$40.7818	$40.78	$40.80	$40.80
Purchase #3	$38.72	11.363%	$43.1198	$43.12	$43.10	$43.10
Purchase #4	$222.93	13.439%	$252.8896	$252.89	$252.90	$252.90
Purchase #5	$61.28	9.681%	$67.2125	$67.21	$67.20	$67.20
Purchase #6	$164.84	13.410%	$186.945	$186.95	$186.95	$186.90
Purchase #7	$132.52	5.547%	$139.8709	$139.87	$139.85	$139.90
7 purchase totals =	$848.59		$935.2872	$935.29	$935.25	$935.30