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	$190.97	9.194%	$208.5278	$208.53	$208.55	$208.50
Purchase #2	$146.32	7.159%	$156.795	$156.80	$156.80	$156.80
Purchase #3	$49.58	10.560%	$54.8156	$54.82	$54.80	$54.80
Purchase #4	$220.73	13.494%	$250.5153	$250.52	$250.50	$250.50
Purchase #5	$100.87	11.587%	$112.5578	$112.56	$112.55	$112.60
Purchase #6	$18.26	11.153%	$20.2965	$20.30	$20.30	$20.30
Purchase #7	$200.36	12.268%	$224.9402	$224.94	$224.95	$224.90
7 purchase totals =	$927.09		$1,028.4482	$1,028.47	$1,028.45	$1,028.40