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 $57.50   9.447%   $62.932   $62.93   $62.95   $62.90  
  Purchase #2 $12.46   6.805%   $13.3079   $13.31   $13.30   $13.30  
  Purchase #3 $181.28   3.844%   $188.2484   $188.25   $188.25   $188.20  
  Purchase #4 $9.60   13.223%   $10.8694   $10.87   $10.85   $10.90  
  Purchase #5 $238.89   12.633%   $269.069   $269.07   $269.05   $269.10  
  Purchase #6 $223.29   7.419%   $239.8559   $239.86   $239.85   $239.90  
  Purchase #7 $230.91   12.257%   $259.2126   $259.21   $259.20   $259.20  
  7 purchase totals = $953.93       $1,043.4952   $1,043.50   $1,043.45   $1,043.50