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	$209.55	12.348%	$235.4252	$235.43	$235.45	$235.40
Purchase #2	$111.77	13.780%	$127.1719	$127.17	$127.15	$127.20
Purchase #3	$108.78	13.572%	$123.5436	$123.54	$123.55	$123.50
Purchase #4	$112.88	4.230%	$117.6548	$117.65	$117.65	$117.70
Purchase #5	$109.38	8.752%	$118.9529	$118.95	$118.95	$119.00
Purchase #6	$97.69	3.496%	$101.1052	$101.11	$101.10	$101.10
Purchase #7	$197.54	12.667%	$222.5624	$222.56	$222.55	$222.60
7 purchase totals =	$947.59		$1,046.4160	$1,046.41	$1,046.40	$1,046.50