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	$12.69	9.283%	$13.868	$13.87	$13.85	$13.90
Purchase #2	$47.66	13.325%	$54.0107	$54.01	$54.00	$54.00
Purchase #3	$136.62	7.273%	$146.5564	$146.56	$146.55	$146.60
Purchase #4	$76.73	13.316%	$86.9474	$86.95	$86.95	$86.90
Purchase #5	$165.44	3.427%	$171.1096	$171.11	$171.10	$171.10
Purchase #6	$151.73	11.159%	$168.6616	$168.66	$168.65	$168.70
Purchase #7	$216.25	10.298%	$238.5194	$238.52	$238.50	$238.50
7 purchase totals =	$807.12		$879.6731	$879.68	$879.60	$879.70