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	$214.45	4.426%	$223.9416	$223.94	$223.95	$223.90
Purchase #2	$120.51	9.307%	$131.7259	$131.73	$131.75	$131.70
Purchase #3	$29.67	12.202%	$33.2903	$33.29	$33.30	$33.30
Purchase #4	$229.92	11.179%	$255.6228	$255.62	$255.60	$255.60
Purchase #5	$202.32	8.665%	$219.851	$219.85	$219.85	$219.90
Purchase #6	$97.72	9.684%	$107.1832	$107.18	$107.20	$107.20
Purchase #7	$163.42	5.797%	$172.8935	$172.89	$172.90	$172.90
7 purchase totals =	$1,058.01		$1,144.5083	$1,144.50	$1,144.55	$1,144.50