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	$202.57	11.190%	$225.2376	$225.24	$225.25	$225.20
Purchase #2	$233.43	12.778%	$263.2577	$263.26	$263.25	$263.30
Purchase #3	$39.39	3.675%	$40.8376	$40.84	$40.85	$40.80
Purchase #4	$182.59	5.270%	$192.2125	$192.21	$192.20	$192.20
Purchase #5	$89.30	11.437%	$99.5132	$99.51	$99.50	$99.50
Purchase #6	$43.92	11.619%	$49.0231	$49.02	$49.00	$49.00
Purchase #7	$215.66	4.694%	$225.7831	$225.78	$225.80	$225.80
7 purchase totals =	$1,006.86		$1,095.8648	$1,095.86	$1,095.85	$1,095.80