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 $163.49   8.247%   $176.973   $176.97   $176.95   $177.00  
  Purchase #2 $162.79   8.331%   $176.352   $176.35   $176.35   $176.40  
  Purchase #3 $58.57   11.465%   $65.2851   $65.29   $65.30   $65.30  
  Purchase #4 $37.78   11.742%   $42.2161   $42.22   $42.20   $42.20  
  Purchase #5 $59.95   12.864%   $67.662   $67.66   $67.65   $67.70  
  Purchase #6 $78.94   6.242%   $83.8674   $83.87   $83.85   $83.90  
  Purchase #7 $162.86   8.287%   $176.3562   $176.36   $176.35   $176.40  
  7 purchase totals = $724.38       $788.7118   $788.72   $788.65   $788.90