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	$245.78	10.109%	$270.6259	$270.63	$270.65	$270.60
Purchase #2	$198.35	11.222%	$220.6088	$220.61	$220.60	$220.60
Purchase #3	$79.82	13.577%	$90.6572	$90.66	$90.65	$90.70
Purchase #4	$178.84	9.226%	$195.3398	$195.34	$195.35	$195.30
Purchase #5	$77.67	4.615%	$81.2545	$81.25	$81.25	$81.30
Purchase #6	$38.83	4.213%	$40.4659	$40.47	$40.45	$40.50
Purchase #7	$216.60	11.548%	$241.613	$241.61	$241.60	$241.60
7 purchase totals =	$1,035.89		$1,140.5651	$1,140.57	$1,140.55	$1,140.60