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 $71.48   5.789%   $75.618   $75.62   $75.60   $75.60  
  Purchase #2 $216.46   8.573%   $235.0171   $235.02   $235.00   $235.00  
  Purchase #3 $230.61   3.124%   $237.8143   $237.81   $237.80   $237.80  
  Purchase #4 $96.39   8.589%   $104.6689   $104.67   $104.65   $104.70  
  Purchase #5 $158.64   13.273%   $179.6963   $179.70   $179.70   $179.70  
  Purchase #6 $41.92   5.184%   $44.0931   $44.09   $44.10   $44.10  
  Purchase #7 $69.74   9.242%   $76.1854   $76.19   $76.20   $76.20  
  7 purchase totals = $885.24       $953.0931   $953.10   $953.05   $953.10