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 $188.68   6.687%   $201.297   $201.30   $201.30   $201.30  
  Purchase #2 $59.72   13.829%   $67.9787   $67.98   $68.00   $68.00  
  Purchase #3 $160.38   10.338%   $176.9601   $176.96   $176.95   $177.00  
  Purchase #4 $159.96   10.839%   $177.2981   $177.30   $177.30   $177.30  
  Purchase #5 $242.68   12.782%   $273.6994   $273.70   $273.70   $273.70  
  Purchase #6 $81.37   7.744%   $87.6713   $87.67   $87.65   $87.70  
  Purchase #7 $225.33   6.758%   $240.5578   $240.56   $240.55   $240.60  
  7 purchase totals = $1,118.12       $1,225.4624   $1,225.47   $1,225.45   $1,225.60