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	$59.84	4.454%	$62.5053	$62.51	$62.50	$62.50
Purchase #2	$21.62	11.133%	$24.027	$24.03	$24.05	$24.00
Purchase #3	$226.46	12.290%	$254.2919	$254.29	$254.30	$254.30
Purchase #4	$241.45	9.381%	$264.1004	$264.10	$264.10	$264.10
Purchase #5	$150.58	9.488%	$164.867	$164.87	$164.85	$164.90
Purchase #6	$76.28	7.830%	$82.2527	$82.25	$82.25	$82.30
Purchase #7	$10.79	9.504%	$11.8155	$11.82	$11.80	$11.80
7 purchase totals =	$787.02		$863.8598	$863.87	$863.85	$863.90