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	$135.31	3.440%	$139.9647	$139.96	$139.95	$140.00
Purchase #2	$5.40	6.694%	$5.7615	$5.76	$5.75	$5.80
Purchase #3	$226.81	6.205%	$240.8836	$240.88	$240.90	$240.90
Purchase #4	$71.54	9.301%	$78.1939	$78.19	$78.20	$78.20
Purchase #5	$52.57	3.873%	$54.606	$54.61	$54.60	$54.60
Purchase #6	$78.64	8.227%	$85.1097	$85.11	$85.10	$85.10
Purchase #7	$131.95	5.786%	$139.5846	$139.58	$139.60	$139.60
7 purchase totals =	$702.22		$744.1040	$744.09	$744.10	$744.20