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 $112.41   11.475%   $125.309   $125.31   $125.30   $125.30  
  Purchase #2 $144.78   4.755%   $151.6643   $151.66   $151.65   $151.70  
  Purchase #3 $46.72   3.622%   $48.4122   $48.41   $48.40   $48.40  
  Purchase #4 $212.81   12.432%   $239.2665   $239.27   $239.25   $239.30  
  Purchase #5 $245.46   6.300%   $260.924   $260.92   $260.90   $260.90  
  Purchase #6 $106.44   6.201%   $113.0403   $113.04   $113.05   $113.00  
  Purchase #7 $143.91   9.130%   $157.049   $157.05   $157.05   $157.00  
  7 purchase totals = $1,012.53       $1,095.6653   $1,095.66   $1,095.60   $1,095.60