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	$8.52	5.395%	$8.9797	$8.98	$9.00	$9.00
Purchase #2	$32.56	10.197%	$35.8801	$35.88	$35.90	$35.90
Purchase #3	$136.89	13.663%	$155.5933	$155.59	$155.60	$155.60
Purchase #4	$245.30	12.872%	$276.875	$276.88	$276.90	$276.90
Purchase #5	$239.83	3.752%	$248.8284	$248.83	$248.85	$248.80
Purchase #6	$177.84	9.848%	$195.3537	$195.35	$195.35	$195.40
Purchase #7	$89.78	5.402%	$94.6299	$94.63	$94.65	$94.60
7 purchase totals =	$930.72		$1,016.1401	$1,016.14	$1,016.25	$1,016.20