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 $83.79   13.377%   $94.9986   $95.00   $95.00   $95.00  
  Purchase #2 $75.79   7.153%   $81.2113   $81.21   $81.20   $81.20  
  Purchase #3 $148.56   12.217%   $166.7096   $166.71   $166.70   $166.70  
  Purchase #4 $104.60   7.692%   $112.6458   $112.65   $112.65   $112.60  
  Purchase #5 $90.57   5.771%   $95.7968   $95.80   $95.80   $95.80  
  Purchase #6 $77.68   12.466%   $87.3636   $87.36   $87.35   $87.40  
  Purchase #7 $246.84   8.866%   $268.7248   $268.72   $268.70   $268.70  
  7 purchase totals = $827.83       $907.4505   $907.45   $907.40   $907.40