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	$78.33	10.864%	$86.8398	$86.84	$86.85	$86.80
Purchase #2	$17.99	4.853%	$18.8631	$18.86	$18.85	$18.90
Purchase #3	$239.66	13.165%	$271.2112	$271.21	$271.20	$271.20
Purchase #4	$11.88	7.596%	$12.7824	$12.78	$12.80	$12.80
Purchase #5	$227.59	6.287%	$241.8986	$241.90	$241.90	$241.90
Purchase #6	$246.91	11.859%	$276.1911	$276.19	$276.20	$276.20
Purchase #7	$196.88	9.604%	$215.7884	$215.79	$215.80	$215.80
7 purchase totals =	$1,019.24		$1,123.5746	$1,123.57	$1,123.60	$1,123.60