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	$139.37	9.364%	$152.4206	$152.42	$152.40	$152.40
Purchase #2	$210.78	6.818%	$225.151	$225.15	$225.15	$225.20
Purchase #3	$198.61	9.523%	$217.5236	$217.52	$217.50	$217.50
Purchase #4	$72.82	5.443%	$76.7836	$76.78	$76.80	$76.80
Purchase #5	$206.78	11.413%	$230.3798	$230.38	$230.40	$230.40
Purchase #6	$12.57	13.177%	$14.2263	$14.23	$14.25	$14.20
Purchase #7	$118.97	4.462%	$124.2784	$124.28	$124.30	$124.30
7 purchase totals =	$959.90		$1,040.7633	$1,040.76	$1,040.80	$1,040.80