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	$143.66	4.637%	$150.3215	$150.32	$150.30	$150.30
Purchase #2	$35.55	5.412%	$37.474	$37.47	$37.45	$37.50
Purchase #3	$40.88	6.519%	$43.545	$43.55	$43.55	$43.50
Purchase #4	$219.35	6.157%	$232.8554	$232.86	$232.85	$232.90
Purchase #5	$196.85	13.535%	$223.4936	$223.49	$223.50	$223.50
Purchase #6	$19.92	4.334%	$20.7833	$20.78	$20.80	$20.80
Purchase #7	$138.98	11.855%	$155.4561	$155.46	$155.45	$155.50
7 purchase totals =	$795.19		$863.9289	$863.93	$863.90	$864.00