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 $57.63   7.706%   $62.071   $62.07   $62.05   $62.10  
  Purchase #2 $202.33   5.116%   $212.6812   $212.68   $212.70   $212.70  
  Purchase #3 $69.27   4.309%   $72.2548   $72.25   $72.25   $72.30  
  Purchase #4 $143.85   12.831%   $162.3074   $162.31   $162.30   $162.30  
  Purchase #5 $181.73   4.678%   $190.2313   $190.23   $190.25   $190.20  
  Purchase #6 $229.31   5.402%   $241.6973   $241.70   $241.70   $241.70  
  Purchase #7 $110.87   4.633%   $116.0066   $116.01   $116.00   $116.00  
  7 purchase totals = $994.99       $1,057.2496   $1,057.25   $1,057.25   $1,057.30