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 $176.51   11.590%   $196.9675   $196.97   $196.95   $197.00  
  Purchase #2 $22.95   12.535%   $25.8268   $25.83   $25.85   $25.80  
  Purchase #3 $156.57   11.601%   $174.7337   $174.73   $174.75   $174.70  
  Purchase #4 $9.93   13.719%   $11.2923   $11.29   $11.30   $11.30  
  Purchase #5 $144.68   4.588%   $151.3179   $151.32   $151.30   $151.30  
  Purchase #6 $133.90   5.332%   $141.0395   $141.04   $141.05   $141.00  
  Purchase #7 $182.74   8.228%   $197.7758   $197.78   $197.80   $197.80  
  7 purchase totals = $827.28       $898.9535   $898.96   $899.00   $898.90