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 $197.63   3.703%   $204.9482   $204.95   $204.95   $204.90  
  Purchase #2 $131.68   4.463%   $137.5569   $137.56   $137.55   $137.60  
  Purchase #3 $76.96   3.317%   $79.5128   $79.51   $79.50   $79.50  
  Purchase #4 $168.64   5.370%   $177.696   $177.70   $177.70   $177.70  
  Purchase #5 $155.48   5.831%   $164.546   $164.55   $164.55   $164.50  
  Purchase #6 $205.41   4.679%   $215.0211   $215.02   $215.00   $215.00  
  Purchase #7 $165.62   10.247%   $182.5911   $182.59   $182.60   $182.60  
  7 purchase totals = $1,101.42       $1,161.8721   $1,161.88   $1,161.85   $1,161.80