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	$80.86	6.204%	$85.8766	$85.88	$85.90	$85.90
Purchase #2	$164.43	4.346%	$171.5761	$171.58	$171.60	$171.60
Purchase #3	$170.60	5.140%	$179.3688	$179.37	$179.35	$179.40
Purchase #4	$203.97	9.254%	$222.8454	$222.85	$222.85	$222.80
Purchase #5	$241.82	4.299%	$252.2158	$252.22	$252.20	$252.20
Purchase #6	$179.41	3.867%	$186.3478	$186.35	$186.35	$186.30
Purchase #7	$152.77	7.591%	$164.3668	$164.37	$164.35	$164.40
7 purchase totals =	$1,193.86		$1,262.5973	$1,262.62	$1,262.60	$1,262.60