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	$48.85	7.578%	$52.5519	$52.55	$52.55	$52.60
Purchase #2	$85.66	10.128%	$94.3356	$94.34	$94.35	$94.30
Purchase #3	$202.72	6.483%	$215.8623	$215.86	$215.85	$215.90
Purchase #4	$218.54	6.832%	$233.4707	$233.47	$233.45	$233.50
Purchase #5	$207.79	4.831%	$217.8283	$217.83	$217.85	$217.80
Purchase #6	$36.41	3.481%	$37.6774	$37.68	$37.70	$37.70
Purchase #7	$216.39	5.260%	$227.7721	$227.77	$227.75	$227.80
7 purchase totals =	$1,016.36		$1,079.4983	$1,079.50	$1,079.50	$1,079.60