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	$208.61	7.618%	$224.5019	$224.50	$224.50	$224.50
Purchase #2	$66.72	7.394%	$71.6533	$71.65	$71.65	$71.70
Purchase #3	$38.90	10.366%	$42.9324	$42.93	$42.95	$42.90
Purchase #4	$239.87	5.255%	$252.4752	$252.48	$252.50	$252.50
Purchase #5	$40.90	11.805%	$45.7282	$45.73	$45.75	$45.70
Purchase #6	$108.30	10.189%	$119.3347	$119.33	$119.35	$119.30
Purchase #7	$155.94	4.368%	$162.7515	$162.75	$162.75	$162.80
7 purchase totals =	$859.24		$919.3772	$919.37	$919.45	$919.40