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	$233.63	9.334%	$255.437	$255.44	$255.45	$255.40
Purchase #2	$111.51	9.613%	$122.2295	$122.23	$122.25	$122.20
Purchase #3	$173.61	10.154%	$191.2384	$191.24	$191.25	$191.20
Purchase #4	$156.70	8.821%	$170.5225	$170.52	$170.50	$170.50
Purchase #5	$111.54	13.794%	$126.9258	$126.93	$126.95	$126.90
Purchase #6	$125.89	4.417%	$131.4506	$131.45	$131.45	$131.50
Purchase #7	$184.78	9.510%	$202.3526	$202.35	$202.35	$202.40
7 purchase totals =	$1,097.66		$1,200.1564	$1,200.16	$1,200.20	$1,200.10