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 $62.26   11.800%   $69.6067   $69.61   $69.60   $69.60  
  Purchase #2 $168.34   4.517%   $175.9439   $175.94   $175.95   $175.90  
  Purchase #3 $129.83   6.223%   $137.9093   $137.91   $137.90   $137.90  
  Purchase #4 $242.29   4.637%   $253.525   $253.53   $253.55   $253.50  
  Purchase #5 $172.26   4.435%   $179.8997   $179.90   $179.90   $179.90  
  Purchase #6 $224.43   6.132%   $238.192   $238.19   $238.20   $238.20  
  Purchase #7 $24.60   4.359%   $25.6723   $25.67   $25.65   $25.70  
  7 purchase totals = $1,024.01       $1,080.7489   $1,080.75   $1,080.75   $1,080.70