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 $41.35   11.840%   $46.2458   $46.25   $46.25   $46.20  
  Purchase #2 $175.27   9.354%   $191.6648   $191.66   $191.65   $191.70  
  Purchase #3 $203.59   6.763%   $217.3588   $217.36   $217.35   $217.40  
  Purchase #4 $228.74   13.573%   $259.7869   $259.79   $259.80   $259.80  
  Purchase #5 $159.99   12.347%   $179.744   $179.74   $179.75   $179.70  
  Purchase #6 $140.40   11.633%   $156.7327   $156.73   $156.75   $156.70  
  Purchase #7 $125.64   8.654%   $136.5129   $136.51   $136.50   $136.50  
  7 purchase totals = $1,074.98       $1,188.0459   $1,188.04   $1,188.05   $1,188.00