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	$121.79	4.233%	$126.9454	$126.95	$126.95	$126.90
Purchase #2	$201.88	9.591%	$221.2423	$221.24	$221.25	$221.20
Purchase #3	$36.92	9.758%	$40.5227	$40.52	$40.50	$40.50
Purchase #4	$27.93	11.845%	$31.2383	$31.24	$31.25	$31.20
Purchase #5	$122.40	4.396%	$127.7807	$127.78	$127.80	$127.80
Purchase #6	$90.41	11.339%	$100.6616	$100.66	$100.65	$100.70
Purchase #7	$181.47	7.445%	$194.9804	$194.98	$195.00	$195.00
7 purchase totals =	$782.80		$843.3714	$843.37	$843.40	$843.30