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	$136.85	3.713%	$141.9312	$141.93	$141.95	$141.90
Purchase #2	$173.64	4.684%	$181.7733	$181.77	$181.75	$181.80
Purchase #3	$73.73	9.201%	$80.5139	$80.51	$80.50	$80.50
Purchase #4	$152.25	8.115%	$164.6051	$164.61	$164.60	$164.60
Purchase #5	$97.35	8.762%	$105.8798	$105.88	$105.90	$105.90
Purchase #6	$90.37	4.462%	$94.4023	$94.40	$94.40	$94.40
Purchase #7	$111.86	10.849%	$123.9957	$124.00	$124.00	$124.00
7 purchase totals =	$836.05		$893.1013	$893.10	$893.10	$893.10