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	$190.93	11.720%	$213.307	$213.31	$213.30	$213.30
Purchase #2	$200.96	7.288%	$215.606	$215.61	$215.60	$215.60
Purchase #3	$49.91	7.430%	$53.6183	$53.62	$53.60	$53.60
Purchase #4	$140.72	10.797%	$155.9135	$155.91	$155.90	$155.90
Purchase #5	$119.98	10.318%	$132.3595	$132.36	$132.35	$132.40
Purchase #6	$116.59	12.395%	$131.0413	$131.04	$131.05	$131.00
Purchase #7	$85.39	12.229%	$95.8323	$95.83	$95.85	$95.80
7 purchase totals =	$904.48		$997.6779	$997.68	$997.65	$997.60