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	$29.83	8.525%	$32.373	$32.37	$32.35	$32.40
Purchase #2	$152.37	3.620%	$157.8858	$157.89	$157.90	$157.90
Purchase #3	$246.40	6.659%	$262.8078	$262.81	$262.80	$262.80
Purchase #4	$197.72	5.243%	$208.0865	$208.09	$208.10	$208.10
Purchase #5	$122.38	7.342%	$131.3651	$131.37	$131.35	$131.40
Purchase #6	$174.69	3.848%	$181.4121	$181.41	$181.40	$181.40
Purchase #7	$131.88	7.805%	$142.1732	$142.17	$142.15	$142.20
7 purchase totals =	$1,055.27		$1,116.1035	$1,116.11	$1,116.05	$1,116.20