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	$218.43	10.497%	$241.3586	$241.36	$241.35	$241.40
Purchase #2	$47.43	3.368%	$49.0274	$49.03	$49.05	$49.00
Purchase #3	$130.73	10.660%	$144.6658	$144.67	$144.65	$144.70
Purchase #4	$197.38	12.174%	$221.409	$221.41	$221.40	$221.40
Purchase #5	$217.31	9.732%	$238.4586	$238.46	$238.45	$238.50
Purchase #6	$63.72	13.528%	$72.34	$72.34	$72.35	$72.30
Purchase #7	$10.25	9.371%	$11.2105	$11.21	$11.20	$11.20
7 purchase totals =	$885.25		$978.4699	$978.48	$978.45	$978.50