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	$187.64	4.576%	$196.2264	$196.23	$196.25	$196.20
Purchase #2	$105.90	7.504%	$113.8467	$113.85	$113.85	$113.80
Purchase #3	$31.35	6.604%	$33.4204	$33.42	$33.40	$33.40
Purchase #4	$196.50	11.757%	$219.6025	$219.60	$219.60	$219.60
Purchase #5	$190.28	13.842%	$216.6186	$216.62	$216.60	$216.60
Purchase #6	$63.32	8.306%	$68.5794	$68.58	$68.60	$68.60
Purchase #7	$215.37	6.142%	$228.598	$228.60	$228.60	$228.60
7 purchase totals =	$990.36		$1,076.8920	$1,076.90	$1,076.90	$1,076.80