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	$118.27	4.445%	$123.5271	$123.53	$123.55	$123.50
Purchase #2	$34.35	9.626%	$37.6565	$37.66	$37.65	$37.70
Purchase #3	$78.45	11.701%	$87.6294	$87.63	$87.65	$87.60
Purchase #4	$36.38	11.112%	$40.4225	$40.42	$40.40	$40.40
Purchase #5	$250.67	9.539%	$274.5814	$274.58	$274.60	$274.60
Purchase #6	$28.45	9.548%	$31.1664	$31.17	$31.15	$31.20
Purchase #7	$57.30	11.450%	$63.8609	$63.86	$63.85	$63.90
7 purchase totals =	$603.87		$658.8442	$658.85	$658.85	$658.90