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	$40.59	6.583%	$43.262	$43.26	$43.25	$43.30
Purchase #2	$245.43	12.539%	$276.2045	$276.20	$276.20	$276.20
Purchase #3	$219.59	13.600%	$249.4542	$249.45	$249.45	$249.50
Purchase #4	$174.90	13.257%	$198.0865	$198.09	$198.10	$198.10
Purchase #5	$117.59	5.165%	$123.6635	$123.66	$123.65	$123.70
Purchase #6	$162.34	10.431%	$179.2737	$179.27	$179.25	$179.30
Purchase #7	$69.88	7.749%	$75.295	$75.30	$75.30	$75.30
7 purchase totals =	$1,030.32		$1,145.2394	$1,145.23	$1,145.20	$1,145.40