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	$131.25	12.821%	$148.0776	$148.08	$148.10	$148.10
Purchase #2	$238.90	6.821%	$255.1954	$255.20	$255.20	$255.20
Purchase #3	$39.49	3.778%	$40.9819	$40.98	$41.00	$41.00
Purchase #4	$62.97	12.862%	$71.0692	$71.07	$71.05	$71.10
Purchase #5	$189.71	10.772%	$210.1456	$210.15	$210.15	$210.10
Purchase #6	$22.60	12.468%	$25.4178	$25.42	$25.40	$25.40
Purchase #7	$190.99	3.103%	$196.9164	$196.92	$196.90	$196.90
7 purchase totals =	$875.91		$947.8039	$947.82	$947.80	$947.80