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	$116.90	5.756%	$123.6288	$123.63	$123.65	$123.60
Purchase #2	$168.81	5.803%	$178.606	$178.61	$178.60	$178.60
Purchase #3	$97.42	8.472%	$105.6734	$105.67	$105.65	$105.70
Purchase #4	$68.79	4.674%	$72.0052	$72.01	$72.00	$72.00
Purchase #5	$83.62	3.193%	$86.29	$86.29	$86.30	$86.30
Purchase #6	$42.70	12.596%	$48.0785	$48.08	$48.10	$48.10
Purchase #7	$171.40	12.802%	$193.3426	$193.34	$193.35	$193.30
7 purchase totals =	$749.64		$807.6245	$807.63	$807.65	$807.60