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 $186.26   5.610%   $196.7092   $196.71   $196.70   $196.70  
  Purchase #2 $149.56   7.217%   $160.3537   $160.35   $160.35   $160.40  
  Purchase #3 $60.96   7.523%   $65.546   $65.55   $65.55   $65.50  
  Purchase #4 $138.98   7.535%   $149.4521   $149.45   $149.45   $149.50  
  Purchase #5 $232.68   12.535%   $261.8464   $261.85   $261.85   $261.80  
  Purchase #6 $165.92   8.214%   $179.5487   $179.55   $179.55   $179.50  
  Purchase #7 $51.32   11.647%   $57.2972   $57.30   $57.30   $57.30  
  7 purchase totals = $985.68       $1,070.7533   $1,070.76   $1,070.75   $1,070.70