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	$93.93	11.110%	$104.3656	$104.37	$104.35	$104.40
Purchase #2	$50.59	11.576%	$56.4463	$56.45	$56.45	$56.40
Purchase #3	$116.78	12.682%	$131.59	$131.59	$131.60	$131.60
Purchase #4	$181.90	12.226%	$204.1391	$204.14	$204.15	$204.10
Purchase #5	$56.58	10.129%	$62.311	$62.31	$62.30	$62.30
Purchase #6	$14.90	4.194%	$15.5249	$15.52	$15.50	$15.50
Purchase #7	$216.63	10.776%	$239.974	$239.97	$239.95	$240.00
7 purchase totals =	$731.31		$814.3509	$814.35	$814.30	$814.30