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 $62.37   10.838%   $69.1297   $69.13   $69.15   $69.10  
  Purchase #2 $215.33   8.471%   $233.5706   $233.57   $233.55   $233.60  
  Purchase #3 $183.60   7.648%   $197.6417   $197.64   $197.65   $197.60  
  Purchase #4 $142.58   8.580%   $154.8134   $154.81   $154.80   $154.80  
  Purchase #5 $219.81   7.254%   $235.755   $235.76   $235.75   $235.80  
  Purchase #6 $180.27   3.419%   $186.4334   $186.43   $186.45   $186.40  
  Purchase #7 $234.61   13.709%   $266.7727   $266.77   $266.75   $266.80  
  7 purchase totals = $1,238.57       $1,344.1165   $1,344.11   $1,344.10   $1,344.10