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	$46.77	11.850%	$52.3122	$52.31	$52.30	$52.30
Purchase #2	$16.72	11.515%	$18.6453	$18.65	$18.65	$18.60
Purchase #3	$131.38	7.209%	$140.8512	$140.85	$140.85	$140.90
Purchase #4	$139.29	10.687%	$154.1759	$154.18	$154.20	$154.20
Purchase #5	$208.75	12.353%	$234.5369	$234.54	$234.55	$234.50
Purchase #6	$85.60	6.173%	$90.8841	$90.88	$90.90	$90.90
Purchase #7	$196.38	4.391%	$205.003	$205.00	$205.00	$205.00
7 purchase totals =	$824.89		$896.4086	$896.41	$896.45	$896.40