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 $107.66   7.824%   $116.0833   $116.08   $116.10   $116.10  
  Purchase #2 $146.62   8.374%   $158.898   $158.90   $158.90   $158.90  
  Purchase #3 $224.34   12.347%   $252.0393   $252.04   $252.05   $252.00  
  Purchase #4 $69.80   5.731%   $73.8002   $73.80   $73.80   $73.80  
  Purchase #5 $112.68   8.296%   $122.0279   $122.03   $122.05   $122.00  
  Purchase #6 $201.27   8.653%   $218.6859   $218.69   $218.70   $218.70  
  Purchase #7 $91.45   3.255%   $94.4267   $94.43   $94.45   $94.40  
  7 purchase totals = $953.82       $1,035.9613   $1,035.97   $1,036.05   $1,035.90