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	$217.85	4.420%	$227.479	$227.48	$227.50	$227.50
Purchase #2	$34.45	7.104%	$36.8973	$36.90	$36.90	$36.90
Purchase #3	$78.43	5.333%	$82.6127	$82.61	$82.60	$82.60
Purchase #4	$72.42	8.446%	$78.5366	$78.54	$78.55	$78.50
Purchase #5	$170.69	4.164%	$177.7975	$177.80	$177.80	$177.80
Purchase #6	$77.96	10.716%	$86.3142	$86.31	$86.30	$86.30
Purchase #7	$7.84	12.640%	$8.831	$8.83	$8.85	$8.80
7 purchase totals =	$659.64		$698.4683	$698.47	$698.50	$698.40