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	$13.33	6.270%	$14.1658	$14.17	$14.15	$14.20
Purchase #2	$46.37	7.215%	$49.7156	$49.72	$49.70	$49.70
Purchase #3	$25.86	5.341%	$27.2412	$27.24	$27.25	$27.20
Purchase #4	$66.31	6.260%	$70.461	$70.46	$70.45	$70.50
Purchase #5	$117.58	12.111%	$131.8201	$131.82	$131.80	$131.80
Purchase #6	$41.68	4.176%	$43.4206	$43.42	$43.40	$43.40
Purchase #7	$180.41	8.207%	$195.2162	$195.22	$195.20	$195.20
7 purchase totals =	$491.54		$532.0405	$532.05	$531.95	$532.00