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	$38.79	4.413%	$40.5018	$40.50	$40.50	$40.50
Purchase #2	$149.76	4.544%	$156.5651	$156.57	$156.55	$156.60
Purchase #3	$232.29	5.606%	$245.3122	$245.31	$245.30	$245.30
Purchase #4	$118.61	4.226%	$123.6225	$123.62	$123.60	$123.60
Purchase #5	$208.48	4.206%	$217.2487	$217.25	$217.25	$217.20
Purchase #6	$81.82	6.773%	$87.3617	$87.36	$87.35	$87.40
Purchase #7	$212.78	6.190%	$225.9511	$225.95	$225.95	$226.00
7 purchase totals =	$1,042.53		$1,096.5631	$1,096.56	$1,096.50	$1,096.60