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	$59.52	8.544%	$64.6054	$64.61	$64.60	$64.60
Purchase #2	$192.97	12.582%	$217.2495	$217.25	$217.25	$217.20
Purchase #3	$132.97	8.641%	$144.4599	$144.46	$144.45	$144.50
Purchase #4	$241.63	7.553%	$259.8803	$259.88	$259.90	$259.90
Purchase #5	$107.82	11.328%	$120.0338	$120.03	$120.05	$120.00
Purchase #6	$129.30	9.361%	$141.4038	$141.40	$141.40	$141.40
Purchase #7	$68.57	5.218%	$72.148	$72.15	$72.15	$72.10
7 purchase totals =	$932.78		$1,019.7807	$1,019.78	$1,019.80	$1,019.70