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	$23.28	4.784%	$24.3937	$24.39	$24.40	$24.40
Purchase #2	$25.47	8.741%	$27.6963	$27.70	$27.70	$27.70
Purchase #3	$92.63	12.147%	$103.8818	$103.88	$103.90	$103.90
Purchase #4	$153.90	10.361%	$169.8456	$169.85	$169.85	$169.80
Purchase #5	$192.73	10.138%	$212.269	$212.27	$212.25	$212.30
Purchase #6	$67.76	5.330%	$71.3716	$71.37	$71.35	$71.40
Purchase #7	$63.56	4.691%	$66.5416	$66.54	$66.55	$66.50
7 purchase totals =	$619.33		$675.9996	$676.00	$676.00	$676.00