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	$49.30	10.659%	$54.5549	$54.55	$54.55	$54.60
Purchase #2	$88.81	5.188%	$93.4175	$93.42	$93.40	$93.40
Purchase #3	$170.67	12.689%	$192.3263	$192.33	$192.35	$192.30
Purchase #4	$222.78	6.534%	$237.3364	$237.34	$237.35	$237.30
Purchase #5	$104.47	10.387%	$115.3213	$115.32	$115.30	$115.30
Purchase #6	$72.67	13.665%	$82.6004	$82.60	$82.60	$82.60
Purchase #7	$217.76	10.794%	$241.265	$241.27	$241.25	$241.30
7 purchase totals =	$926.46		$1,016.8218	$1,016.83	$1,016.80	$1,016.80