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 $86.37   13.476%   $98.0092   $98.01   $98.00   $98.00  
  Purchase #2 $131.62   13.735%   $149.698   $149.70   $149.70   $149.70  
  Purchase #3 $218.89   8.406%   $237.2899   $237.29   $237.30   $237.30  
  Purchase #4 $82.77   5.531%   $87.348   $87.35   $87.35   $87.30  
  Purchase #5 $227.52   13.420%   $258.0532   $258.05   $258.05   $258.10  
  Purchase #6 $140.81   3.581%   $145.8524   $145.85   $145.85   $145.90  
  Purchase #7 $232.55   11.133%   $258.4398   $258.44   $258.45   $258.40  
  7 purchase totals = $1,120.53       $1,234.6905   $1,234.69   $1,234.70   $1,234.70