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	$125.83	12.341%	$141.3587	$141.36	$141.35	$141.40
Purchase #2	$189.28	12.742%	$213.3981	$213.40	$213.40	$213.40
Purchase #3	$230.91	12.819%	$260.5104	$260.51	$260.50	$260.50
Purchase #4	$29.25	12.486%	$32.9022	$32.90	$32.90	$32.90
Purchase #5	$42.98	8.105%	$46.4635	$46.46	$46.45	$46.50
Purchase #6	$124.90	13.746%	$142.0688	$142.07	$142.05	$142.10
Purchase #7	$84.74	12.856%	$95.6342	$95.63	$95.65	$95.60
7 purchase totals =	$827.89		$932.3359	$932.33	$932.30	$932.40