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	$201.67	11.683%	$225.2311	$225.23	$225.25	$225.20
Purchase #2	$140.66	8.268%	$152.2898	$152.29	$152.30	$152.30
Purchase #3	$225.60	8.339%	$244.4128	$244.41	$244.40	$244.40
Purchase #4	$182.89	8.705%	$198.8106	$198.81	$198.80	$198.80
Purchase #5	$30.38	8.299%	$32.9012	$32.90	$32.90	$32.90
Purchase #6	$145.91	8.596%	$158.4524	$158.45	$158.45	$158.50
Purchase #7	$228.39	4.450%	$238.5534	$238.55	$238.55	$238.60
7 purchase totals =	$1,155.50		$1,250.6513	$1,250.64	$1,250.65	$1,250.70