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	$116.32	6.140%	$123.462	$123.46	$123.45	$123.50
Purchase #2	$72.82	13.252%	$82.4701	$82.47	$82.45	$82.50
Purchase #3	$90.58	12.655%	$102.0429	$102.04	$102.05	$102.00
Purchase #4	$25.62	3.555%	$26.5308	$26.53	$26.55	$26.50
Purchase #5	$85.74	4.549%	$89.6403	$89.64	$89.65	$89.60
Purchase #6	$96.45	12.840%	$108.8342	$108.83	$108.85	$108.80
Purchase #7	$157.60	7.147%	$168.8637	$168.86	$168.85	$168.90
7 purchase totals =	$645.13		$701.8440	$701.83	$701.85	$701.80