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	$78.68	9.802%	$86.3922	$86.39	$86.40	$86.40
Purchase #2	$80.41	12.185%	$90.208	$90.21	$90.20	$90.20
Purchase #3	$54.33	9.828%	$59.6696	$59.67	$59.65	$59.70
Purchase #4	$217.82	12.252%	$244.5073	$244.51	$244.50	$244.50
Purchase #5	$36.81	3.175%	$37.9787	$37.98	$38.00	$38.00
Purchase #6	$29.58	11.673%	$33.0329	$33.03	$33.05	$33.00
Purchase #7	$57.58	3.295%	$59.4773	$59.48	$59.50	$59.50
7 purchase totals =	$555.21		$611.2660	$611.27	$611.30	$611.30