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 $184.29   7.240%   $197.6326   $197.63   $197.65   $197.60  
  Purchase #2 $184.48   6.503%   $196.4767   $196.48   $196.50   $196.50  
  Purchase #3 $53.63   7.469%   $57.6356   $57.64   $57.65   $57.60  
  Purchase #4 $199.27   3.262%   $205.7702   $205.77   $205.75   $205.80  
  Purchase #5 $112.64   11.746%   $125.8707   $125.87   $125.85   $125.90  
  Purchase #6 $97.91   3.207%   $101.05   $101.05   $101.05   $101.10  
  Purchase #7 $93.30   9.293%   $101.9704   $101.97   $101.95   $102.00  
  7 purchase totals = $925.52       $986.4062   $986.41   $986.40   $986.50