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	$200.25	10.859%	$221.9951	$222.00	$222.00	$222.00
Purchase #2	$229.61	12.515%	$258.3457	$258.35	$258.35	$258.30
Purchase #3	$21.79	9.658%	$23.8945	$23.89	$23.90	$23.90
Purchase #4	$180.78	5.590%	$190.8856	$190.89	$190.90	$190.90
Purchase #5	$40.75	11.693%	$45.5149	$45.51	$45.50	$45.50
Purchase #6	$134.86	3.527%	$139.6165	$139.62	$139.60	$139.60
Purchase #7	$131.50	9.194%	$143.5901	$143.59	$143.60	$143.60
7 purchase totals =	$939.54		$1,023.8424	$1,023.85	$1,023.85	$1,023.80