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	$193.77	12.189%	$217.3886	$217.39	$217.40	$217.40
Purchase #2	$72.51	12.279%	$81.4135	$81.41	$81.40	$81.40
Purchase #3	$38.78	4.204%	$40.4103	$40.41	$40.40	$40.40
Purchase #4	$196.78	7.151%	$210.8517	$210.85	$210.85	$210.90
Purchase #5	$24.94	11.390%	$27.7807	$27.78	$27.80	$27.80
Purchase #6	$41.42	4.764%	$43.3932	$43.39	$43.40	$43.40
Purchase #7	$149.81	11.660%	$167.2778	$167.28	$167.30	$167.30
7 purchase totals =	$718.01		$788.5158	$788.51	$788.55	$788.60