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 $59.30   5.512%   $62.5686   $62.57   $62.55   $62.60  
  Purchase #2 $74.50   6.356%   $79.2352   $79.24   $79.25   $79.20  
  Purchase #3 $186.81   3.701%   $193.7238   $193.72   $193.70   $193.70  
  Purchase #4 $190.62   7.708%   $205.313   $205.31   $205.30   $205.30  
  Purchase #5 $169.57   5.567%   $179.01   $179.01   $179.00   $179.00  
  Purchase #6 $54.60   3.819%   $56.6852   $56.69   $56.70   $56.70  
  Purchase #7 $232.37   11.608%   $259.3435   $259.34   $259.35   $259.30  
  7 purchase totals = $967.77       $1,035.8793   $1,035.88   $1,035.85   $1,035.80