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 $60.65   11.192%   $67.4379   $67.44   $67.45   $67.40  
  Purchase #2 $196.66   6.626%   $209.6907   $209.69   $209.70   $209.70  
  Purchase #3 $22.80   9.634%   $24.9966   $25.00   $25.00   $25.00  
  Purchase #4 $206.27   8.152%   $223.0851   $223.09   $223.10   $223.10  
  Purchase #5 $110.62   10.596%   $122.3413   $122.34   $122.35   $122.30  
  Purchase #6 $242.75   12.643%   $273.4409   $273.44   $273.45   $273.40  
  Purchase #7 $122.39   10.795%   $135.602   $135.60   $135.60   $135.60  
  7 purchase totals = $962.14       $1,056.5945   $1,056.60   $1,056.65   $1,056.50