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 $86.95   11.597%   $97.0336   $97.03   $97.05   $97.00  
  Purchase #2 $52.93   3.275%   $54.6635   $54.66   $54.65   $54.70  
  Purchase #3 $7.76   5.775%   $8.2081   $8.21   $8.20   $8.20  
  Purchase #4 $191.32   7.399%   $205.4758   $205.48   $205.50   $205.50  
  Purchase #5 $168.28   10.216%   $185.4715   $185.47   $185.45   $185.50  
  Purchase #6 $219.57   4.861%   $230.2433   $230.24   $230.25   $230.20  
  Purchase #7 $154.58   10.540%   $170.8727   $170.87   $170.85   $170.90  
  7 purchase totals = $881.39       $951.9685   $951.96   $951.95   $952.00