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 $226.66   5.492%   $239.1082   $239.11   $239.10   $239.10  
  Purchase #2 $101.54   6.837%   $108.4823   $108.48   $108.50   $108.50  
  Purchase #3 $157.66   7.553%   $169.5681   $169.57   $169.55   $169.60  
  Purchase #4 $216.49   4.790%   $226.8599   $226.86   $226.85   $226.90  
  Purchase #5 $214.54   9.628%   $235.1959   $235.20   $235.20   $235.20  
  Purchase #6 $53.64   9.733%   $58.8608   $58.86   $58.85   $58.90  
  Purchase #7 $53.80   5.593%   $56.809   $56.81   $56.80   $56.80  
  7 purchase totals = $1,024.33       $1,094.8842   $1,094.89   $1,094.85   $1,095.00