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 $133.66   5.472%   $140.9739   $140.97   $140.95   $141.00  
  Purchase #2 $209.85   3.787%   $217.797   $217.80   $217.80   $217.80  
  Purchase #3 $192.47   5.308%   $202.6863   $202.69   $202.70   $202.70  
  Purchase #4 $136.50   9.531%   $149.5098   $149.51   $149.50   $149.50  
  Purchase #5 $206.73   8.834%   $224.9925   $224.99   $225.00   $225.00  
  Purchase #6 $51.75   11.356%   $57.6267   $57.63   $57.65   $57.60  
  Purchase #7 $126.37   3.719%   $131.0697   $131.07   $131.05   $131.10  
  7 purchase totals = $1,057.33       $1,124.6559   $1,124.66   $1,124.65   $1,124.70