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	$144.62	9.674%	$158.6105	$158.61	$158.60	$158.60
Purchase #2	$111.32	3.822%	$115.5747	$115.57	$115.55	$115.60
Purchase #3	$41.90	8.392%	$45.4162	$45.42	$45.40	$45.40
Purchase #4	$186.77	5.443%	$196.9359	$196.94	$196.95	$196.90
Purchase #5	$206.84	9.420%	$226.3243	$226.32	$226.30	$226.30
Purchase #6	$5.66	6.427%	$6.0238	$6.02	$6.00	$6.00
Purchase #7	$126.37	4.131%	$131.5903	$131.59	$131.60	$131.60
7 purchase totals =	$823.48		$880.4757	$880.47	$880.40	$880.40