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	$202.42	7.869%	$218.3484	$218.35	$218.35	$218.30
Purchase #2	$33.93	10.454%	$37.477	$37.48	$37.50	$37.50
Purchase #3	$162.72	6.500%	$173.2968	$173.30	$173.30	$173.30
Purchase #4	$187.95	8.581%	$204.078	$204.08	$204.10	$204.10
Purchase #5	$206.64	10.195%	$227.7069	$227.71	$227.70	$227.70
Purchase #6	$176.46	8.205%	$190.9385	$190.94	$190.95	$190.90
Purchase #7	$68.54	4.605%	$71.6963	$71.70	$71.70	$71.70
7 purchase totals =	$1,038.66		$1,123.5419	$1,123.56	$1,123.60	$1,123.50