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	$100.92	12.679%	$113.7156	$113.72	$113.70	$113.70
Purchase #2	$219.29	7.557%	$235.8617	$235.86	$235.85	$235.90
Purchase #3	$100.45	10.595%	$111.0927	$111.09	$111.10	$111.10
Purchase #4	$20.68	3.682%	$21.4414	$21.44	$21.45	$21.40
Purchase #5	$203.88	12.525%	$229.416	$229.42	$229.40	$229.40
Purchase #6	$202.96	5.517%	$214.1573	$214.16	$214.15	$214.20
Purchase #7	$99.53	4.360%	$103.8695	$103.87	$103.85	$103.90
7 purchase totals =	$947.71		$1,029.5542	$1,029.56	$1,029.50	$1,029.60