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	$117.38	12.147%	$131.6381	$131.64	$131.65	$131.60
Purchase #2	$152.26	6.870%	$162.7203	$162.72	$162.70	$162.70
Purchase #3	$92.88	13.841%	$105.7355	$105.74	$105.75	$105.70
Purchase #4	$141.86	8.181%	$153.4656	$153.47	$153.45	$153.50
Purchase #5	$152.39	11.456%	$169.8478	$169.85	$169.85	$169.80
Purchase #6	$49.93	11.372%	$55.608	$55.61	$55.60	$55.60
Purchase #7	$198.87	12.155%	$223.0426	$223.04	$223.05	$223.00
7 purchase totals =	$905.57		$1,002.0579	$1,002.07	$1,002.05	$1,001.90