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	$36.54	3.602%	$37.8562	$37.86	$37.85	$37.90
Purchase #2	$191.38	13.698%	$217.5952	$217.60	$217.60	$217.60
Purchase #3	$43.81	4.601%	$45.8257	$45.83	$45.85	$45.80
Purchase #4	$173.81	12.755%	$195.9795	$195.98	$196.00	$196.00
Purchase #5	$236.82	5.288%	$249.343	$249.34	$249.35	$249.30
Purchase #6	$127.26	9.209%	$138.9794	$138.98	$139.00	$139.00
Purchase #7	$119.85	5.459%	$126.3926	$126.39	$126.40	$126.40
7 purchase totals =	$929.47		$1,011.9716	$1,011.98	$1,012.05	$1,012.00