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	$31.54	7.562%	$33.9251	$33.93	$33.95	$33.90
Purchase #2	$161.53	4.380%	$168.605	$168.61	$168.60	$168.60
Purchase #3	$197.84	10.332%	$218.2808	$218.28	$218.30	$218.30
Purchase #4	$203.34	6.730%	$217.0248	$217.02	$217.00	$217.00
Purchase #5	$45.27	12.847%	$51.0858	$51.09	$51.10	$51.10
Purchase #6	$81.30	9.555%	$89.0682	$89.07	$89.05	$89.10
Purchase #7	$223.37	3.792%	$231.8402	$231.84	$231.85	$231.80
7 purchase totals =	$944.19		$1,009.8299	$1,009.84	$1,009.85	$1,009.80