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	$244.46	12.718%	$275.5504	$275.55	$275.55	$275.60
Purchase #2	$141.32	13.384%	$160.2343	$160.23	$160.25	$160.20
Purchase #3	$183.68	3.330%	$189.7965	$189.80	$189.80	$189.80
Purchase #4	$49.31	5.189%	$51.8687	$51.87	$51.85	$51.90
Purchase #5	$248.42	10.610%	$274.7774	$274.78	$274.80	$274.80
Purchase #6	$31.56	3.102%	$32.539	$32.54	$32.55	$32.50
Purchase #7	$36.25	3.842%	$37.6427	$37.64	$37.65	$37.60
7 purchase totals =	$935.00		$1,022.4090	$1,022.41	$1,022.45	$1,022.40