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 $41.41   5.433%   $43.6598   $43.66   $43.65   $43.70  
  Purchase #2 $210.95   10.541%   $233.1862   $233.19   $233.20   $233.20  
  Purchase #3 $143.94   5.190%   $151.4105   $151.41   $151.40   $151.40  
  Purchase #4 $141.26   5.817%   $149.4771   $149.48   $149.50   $149.50  
  Purchase #5 $17.89   11.530%   $19.9527   $19.95   $19.95   $20.00  
  Purchase #6 $192.96   6.600%   $205.6954   $205.70   $205.70   $205.70  
  Purchase #7 $241.26   9.453%   $264.0663   $264.07   $264.05   $264.10  
  7 purchase totals = $989.67       $1,067.4480   $1,067.46   $1,067.45   $1,067.60