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	$205.87	12.838%	$232.2996	$232.30	$232.30	$232.30
Purchase #2	$11.85	3.281%	$12.2388	$12.24	$12.25	$12.20
Purchase #3	$229.45	6.622%	$244.6442	$244.64	$244.65	$244.60
Purchase #4	$71.45	9.480%	$78.2235	$78.22	$78.20	$78.20
Purchase #5	$202.32	12.360%	$227.3268	$227.33	$227.35	$227.30
Purchase #6	$186.69	6.355%	$198.5541	$198.55	$198.55	$198.60
Purchase #7	$37.41	7.449%	$40.1967	$40.20	$40.20	$40.20
7 purchase totals =	$945.04		$1,033.4837	$1,033.48	$1,033.50	$1,033.40