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	$129.94	9.620%	$142.4402	$142.44	$142.45	$142.40
Purchase #2	$84.47	9.349%	$92.3671	$92.37	$92.35	$92.40
Purchase #3	$40.54	13.665%	$46.0798	$46.08	$46.10	$46.10
Purchase #4	$155.30	7.753%	$167.3404	$167.34	$167.35	$167.30
Purchase #5	$63.95	6.170%	$67.8957	$67.90	$67.90	$67.90
Purchase #6	$81.59	10.249%	$89.9522	$89.95	$89.95	$90.00
Purchase #7	$53.87	3.613%	$55.8163	$55.82	$55.80	$55.80
7 purchase totals =	$609.66		$661.8917	$661.90	$661.90	$661.90