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 $113.58   10.722%   $125.758   $125.76   $125.75   $125.80  
  Purchase #2 $171.61   7.378%   $184.2714   $184.27   $184.25   $184.30  
  Purchase #3 $138.87   5.614%   $146.6662   $146.67   $146.65   $146.70  
  Purchase #4 $84.84   6.850%   $90.6515   $90.65   $90.65   $90.70  
  Purchase #5 $244.83   9.469%   $268.013   $268.01   $268.00   $268.00  
  Purchase #6 $119.79   4.823%   $125.5675   $125.57   $125.55   $125.60  
  Purchase #7 $165.71   8.120%   $179.1657   $179.17   $179.15   $179.20  
  7 purchase totals = $1,039.23       $1,120.0933   $1,120.10   $1,120.00   $1,120.30