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	$61.85	10.455%	$68.3164	$68.32	$68.30	$68.30
Purchase #2	$178.46	7.809%	$192.3959	$192.40	$192.40	$192.40
Purchase #3	$140.71	4.819%	$147.4908	$147.49	$147.50	$147.50
Purchase #4	$161.85	3.106%	$166.8771	$166.88	$166.90	$166.90
Purchase #5	$217.70	10.309%	$240.1427	$240.14	$240.15	$240.10
Purchase #6	$69.97	5.523%	$73.8344	$73.83	$73.85	$73.80
Purchase #7	$180.47	8.776%	$196.308	$196.31	$196.30	$196.30
7 purchase totals =	$1,011.01		$1,085.3653	$1,085.37	$1,085.40	$1,085.30