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	$168.43	4.385%	$175.8157	$175.82	$175.80	$175.80
Purchase #2	$14.65	8.766%	$15.9342	$15.93	$15.95	$15.90
Purchase #3	$214.46	13.703%	$243.8475	$243.85	$243.85	$243.80
Purchase #4	$27.56	12.614%	$31.0364	$31.04	$31.05	$31.00
Purchase #5	$37.27	3.591%	$38.6084	$38.61	$38.60	$38.60
Purchase #6	$150.39	4.366%	$156.956	$156.96	$156.95	$157.00
Purchase #7	$106.77	5.465%	$112.605	$112.61	$112.60	$112.60
7 purchase totals =	$719.53		$774.8032	$774.82	$774.80	$774.70