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 $85.51   8.206%   $92.527   $92.53   $92.55   $92.50  
  Purchase #2 $126.73   6.508%   $134.9776   $134.98   $135.00   $135.00  
  Purchase #3 $190.86   7.575%   $205.3176   $205.32   $205.30   $205.30  
  Purchase #4 $41.72   9.515%   $45.6897   $45.69   $45.70   $45.70  
  Purchase #5 $236.66   5.250%   $249.0847   $249.08   $249.10   $249.10  
  Purchase #6 $26.38   5.546%   $27.843   $27.84   $27.85   $27.80  
  Purchase #7 $179.58   7.263%   $192.6229   $192.62   $192.60   $192.60  
  7 purchase totals = $887.44       $948.0625   $948.06   $948.10   $948.00