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	$41.66	5.141%	$43.8017	$43.80	$43.80	$43.80
Purchase #2	$112.90	4.402%	$117.8699	$117.87	$117.85	$117.90
Purchase #3	$133.91	7.857%	$144.4313	$144.43	$144.45	$144.40
Purchase #4	$221.71	10.872%	$245.8143	$245.81	$245.80	$245.80
Purchase #5	$100.98	3.862%	$104.8798	$104.88	$104.90	$104.90
Purchase #6	$206.79	13.767%	$235.2588	$235.26	$235.25	$235.30
Purchase #7	$240.83	9.872%	$264.6047	$264.60	$264.60	$264.60
7 purchase totals =	$1,058.78		$1,156.6605	$1,156.65	$1,156.65	$1,156.70