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	$213.58	10.468%	$235.9376	$235.94	$235.95	$235.90
Purchase #2	$153.43	3.343%	$158.5592	$158.56	$158.55	$158.60
Purchase #3	$86.33	4.296%	$90.0387	$90.04	$90.05	$90.00
Purchase #4	$206.39	13.453%	$234.1556	$234.16	$234.15	$234.20
Purchase #5	$131.45	7.410%	$141.1904	$141.19	$141.20	$141.20
Purchase #6	$37.88	6.765%	$40.4426	$40.44	$40.45	$40.40
Purchase #7	$150.28	6.115%	$159.4696	$159.47	$159.45	$159.50
7 purchase totals =	$979.34		$1,059.7937	$1,059.80	$1,059.80	$1,059.80