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	$121.75	7.516%	$130.9007	$130.90	$130.90	$130.90
Purchase #2	$70.85	10.602%	$78.3615	$78.36	$78.35	$78.40
Purchase #3	$57.89	12.411%	$65.0747	$65.07	$65.05	$65.10
Purchase #4	$34.25	3.583%	$35.4772	$35.48	$35.50	$35.50
Purchase #5	$197.29	10.481%	$217.968	$217.97	$217.95	$218.00
Purchase #6	$131.39	4.105%	$136.7836	$136.78	$136.80	$136.80
Purchase #7	$178.67	3.745%	$185.3612	$185.36	$185.35	$185.40
7 purchase totals =	$792.09		$849.9269	$849.92	$849.90	$850.10