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 $33.66   5.852%   $35.6298   $35.63   $35.65   $35.60  
  Purchase #2 $66.51   4.233%   $69.3254   $69.33   $69.35   $69.30  
  Purchase #3 $59.34   13.609%   $67.4156   $67.42   $67.40   $67.40  
  Purchase #4 $10.26   13.586%   $11.6539   $11.65   $11.65   $11.70  
  Purchase #5 $107.26   4.139%   $111.6995   $111.70   $111.70   $111.70  
  Purchase #6 $102.64   13.623%   $116.6226   $116.62   $116.60   $116.60  
  Purchase #7 $197.47   7.576%   $212.4303   $212.43   $212.45   $212.40  
  7 purchase totals = $577.14       $624.7771   $624.78   $624.80   $624.70