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	$105.48	10.789%	$116.8602	$116.86	$116.85	$116.90
Purchase #2	$83.89	4.853%	$87.9612	$87.96	$87.95	$88.00
Purchase #3	$167.57	3.403%	$173.2724	$173.27	$173.25	$173.30
Purchase #4	$178.27	11.222%	$198.2755	$198.28	$198.30	$198.30
Purchase #5	$101.83	11.870%	$113.9172	$113.92	$113.90	$113.90
Purchase #6	$69.36	9.401%	$75.8805	$75.88	$75.90	$75.90
Purchase #7	$71.72	12.132%	$80.4211	$80.42	$80.40	$80.40
7 purchase totals =	$778.12		$846.5881	$846.59	$846.55	$846.70