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	$131.70	12.244%	$147.8253	$147.83	$147.85	$147.80
Purchase #2	$116.51	9.451%	$127.5214	$127.52	$127.50	$127.50
Purchase #3	$6.93	5.493%	$7.3107	$7.31	$7.30	$7.30
Purchase #4	$22.51	13.179%	$25.4766	$25.48	$25.50	$25.50
Purchase #5	$213.82	13.766%	$243.2545	$243.25	$243.25	$243.30
Purchase #6	$8.44	4.715%	$8.8379	$8.84	$8.85	$8.80
Purchase #7	$162.38	9.728%	$178.1763	$178.18	$178.20	$178.20
7 purchase totals =	$662.29		$738.4027	$738.41	$738.45	$738.40