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	$46.61	10.114%	$51.3241	$51.32	$51.30	$51.30
Purchase #2	$211.72	4.186%	$220.5826	$220.58	$220.60	$220.60
Purchase #3	$6.27	5.133%	$6.5918	$6.59	$6.60	$6.60
Purchase #4	$38.49	10.105%	$42.3794	$42.38	$42.40	$42.40
Purchase #5	$33.57	10.172%	$36.9847	$36.98	$37.00	$37.00
Purchase #6	$109.38	6.835%	$116.8561	$116.86	$116.85	$116.90
Purchase #7	$116.96	13.483%	$132.7297	$132.73	$132.75	$132.70
7 purchase totals =	$563.00		$607.4484	$607.44	$607.50	$607.50