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	$184.34	8.160%	$199.3821	$199.38	$199.40	$199.40
Purchase #2	$77.80	5.677%	$82.2167	$82.22	$82.20	$82.20
Purchase #3	$115.77	9.795%	$127.1097	$127.11	$127.10	$127.10
Purchase #4	$13.27	4.833%	$13.9113	$13.91	$13.90	$13.90
Purchase #5	$210.87	13.284%	$238.882	$238.88	$238.90	$238.90
Purchase #6	$46.93	11.351%	$52.257	$52.26	$52.25	$52.30
Purchase #7	$87.54	12.618%	$98.5858	$98.59	$98.60	$98.60
7 purchase totals =	$736.52		$812.3446	$812.35	$812.35	$812.40