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	$127.37	9.465%	$139.4256	$139.43	$139.45	$139.40
Purchase #2	$166.66	10.776%	$184.6193	$184.62	$184.60	$184.60
Purchase #3	$39.35	11.327%	$43.8072	$43.81	$43.80	$43.80
Purchase #4	$212.44	3.534%	$219.9476	$219.95	$219.95	$219.90
Purchase #5	$101.59	10.293%	$112.0467	$112.05	$112.05	$112.00
Purchase #6	$112.35	4.418%	$117.3136	$117.31	$117.30	$117.30
Purchase #7	$180.36	9.119%	$196.807	$196.81	$196.80	$196.80
7 purchase totals =	$940.12		$1,013.9670	$1,013.98	$1,013.95	$1,013.80