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 $60.44   3.821%   $62.7494   $62.75   $62.75   $62.70  
  Purchase #2 $235.95   6.723%   $251.8129   $251.81   $251.80   $251.80  
  Purchase #3 $106.85   10.289%   $117.8438   $117.84   $117.85   $117.80  
  Purchase #4 $62.48   11.793%   $69.8483   $69.85   $69.85   $69.80  
  Purchase #5 $187.53   9.626%   $205.5816   $205.58   $205.60   $205.60  
  Purchase #6 $235.33   10.560%   $260.1808   $260.18   $260.20   $260.20  
  Purchase #7 $76.54   10.705%   $84.7336   $84.73   $84.75   $84.70  
  7 purchase totals = $965.12       $1,052.7504   $1,052.74   $1,052.80   $1,052.60