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	$245.34	10.567%	$271.2651	$271.27	$271.25	$271.30
Purchase #2	$78.30	3.454%	$81.0045	$81.00	$81.00	$81.00
Purchase #3	$43.51	5.292%	$45.8125	$45.81	$45.80	$45.80
Purchase #4	$52.79	13.387%	$59.857	$59.86	$59.85	$59.90
Purchase #5	$102.78	13.310%	$116.46	$116.46	$116.45	$116.50
Purchase #6	$193.52	12.333%	$217.3868	$217.39	$217.40	$217.40
Purchase #7	$120.94	4.749%	$126.6834	$126.68	$126.70	$126.70
7 purchase totals =	$837.18		$918.4693	$918.47	$918.45	$918.60