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	$52.71	13.483%	$59.8169	$59.82	$59.80	$59.80
Purchase #2	$195.56	5.456%	$206.2298	$206.23	$206.25	$206.20
Purchase #3	$48.83	4.789%	$51.1685	$51.17	$51.15	$51.20
Purchase #4	$186.60	9.563%	$204.4446	$204.44	$204.45	$204.40
Purchase #5	$220.45	3.311%	$227.7491	$227.75	$227.75	$227.70
Purchase #6	$148.67	6.483%	$158.3083	$158.31	$158.30	$158.30
Purchase #7	$32.30	10.127%	$35.571	$35.57	$35.55	$35.60
7 purchase totals =	$885.12		$943.2882	$943.29	$943.25	$943.20