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	$241.88	4.227%	$252.1043	$252.10	$252.10	$252.10
Purchase #2	$90.88	9.429%	$99.4491	$99.45	$99.45	$99.40
Purchase #3	$152.25	10.265%	$167.8785	$167.88	$167.90	$167.90
Purchase #4	$203.74	6.828%	$217.6514	$217.65	$217.65	$217.70
Purchase #5	$126.97	3.511%	$131.4279	$131.43	$131.45	$131.40
Purchase #6	$200.56	9.390%	$219.3926	$219.39	$219.40	$219.40
Purchase #7	$177.86	10.705%	$196.8999	$196.90	$196.90	$196.90
7 purchase totals =	$1,194.14		$1,284.8037	$1,284.80	$1,284.85	$1,284.80