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	$96.57	9.584%	$105.8253	$105.83	$105.85	$105.80
Purchase #2	$230.64	13.373%	$261.4835	$261.48	$261.50	$261.50
Purchase #3	$53.94	3.735%	$55.9547	$55.95	$55.95	$56.00
Purchase #4	$211.74	13.854%	$241.0745	$241.07	$241.05	$241.10
Purchase #5	$5.52	12.534%	$6.2119	$6.21	$6.20	$6.20
Purchase #6	$131.57	3.540%	$136.2276	$136.23	$136.25	$136.20
Purchase #7	$245.89	13.401%	$278.8417	$278.84	$278.85	$278.80
7 purchase totals =	$975.87		$1,085.6192	$1,085.61	$1,085.65	$1,085.60