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 $202.53   4.469%   $211.5811   $211.58   $211.60   $211.60  
  Purchase #2 $244.48   11.191%   $271.8398   $271.84   $271.85   $271.80  
  Purchase #3 $249.84   9.738%   $274.1694   $274.17   $274.15   $274.20  
  Purchase #4 $52.77   13.584%   $59.9383   $59.94   $59.95   $59.90  
  Purchase #5 $238.93   8.476%   $259.1817   $259.18   $259.20   $259.20  
  Purchase #6 $218.71   9.204%   $238.8401   $238.84   $238.85   $238.80  
  Purchase #7 $144.72   4.843%   $151.7288   $151.73   $151.75   $151.70  
  7 purchase totals = $1,351.98       $1,467.2792   $1,467.28   $1,467.35   $1,467.20