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	$78.35	9.174%	$85.5378	$85.54	$85.55	$85.50
Purchase #2	$135.60	12.177%	$152.112	$152.11	$152.10	$152.10
Purchase #3	$126.44	4.165%	$131.7062	$131.71	$131.70	$131.70
Purchase #4	$151.82	10.461%	$167.7019	$167.70	$167.70	$167.70
Purchase #5	$140.39	7.762%	$151.2871	$151.29	$151.30	$151.30
Purchase #6	$193.40	13.567%	$219.6386	$219.64	$219.65	$219.60
Purchase #7	$163.66	9.558%	$179.3026	$179.30	$179.30	$179.30
7 purchase totals =	$989.66		$1,087.2862	$1,087.29	$1,087.30	$1,087.20