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	$143.40	10.468%	$158.4111	$158.41	$158.40	$158.40
Purchase #2	$51.78	8.868%	$56.3719	$56.37	$56.35	$56.40
Purchase #3	$176.69	6.168%	$187.5882	$187.59	$187.60	$187.60
Purchase #4	$147.80	6.375%	$157.2223	$157.22	$157.20	$157.20
Purchase #5	$136.83	13.412%	$155.1816	$155.18	$155.20	$155.20
Purchase #6	$250.63	6.640%	$267.2718	$267.27	$267.25	$267.30
Purchase #7	$63.89	4.699%	$66.8922	$66.89	$66.90	$66.90
7 purchase totals =	$971.02		$1,048.9391	$1,048.93	$1,048.90	$1,049.00