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 $184.68   5.561%   $194.9501   $194.95   $194.95   $195.00  
  Purchase #2 $82.77   10.699%   $91.6256   $91.63   $91.65   $91.60  
  Purchase #3 $132.39   5.801%   $140.0699   $140.07   $140.05   $140.10  
  Purchase #4 $49.66   5.830%   $52.5552   $52.56   $52.55   $52.60  
  Purchase #5 $56.29   13.526%   $63.9038   $63.90   $63.90   $63.90  
  Purchase #6 $27.72   6.441%   $29.5054   $29.51   $29.50   $29.50  
  Purchase #7 $117.83   9.643%   $129.1923   $129.19   $129.20   $129.20  
  7 purchase totals = $651.34       $701.8023   $701.81   $701.80   $701.90