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 $58.84   4.740%   $61.629   $61.63   $61.65   $61.60  
  Purchase #2 $201.46   13.336%   $228.3267   $228.33   $228.35   $228.30  
  Purchase #3 $125.66   4.394%   $131.1815   $131.18   $131.20   $131.20  
  Purchase #4 $121.63   6.842%   $129.9519   $129.95   $129.95   $130.00  
  Purchase #5 $51.90   5.368%   $54.686   $54.69   $54.70   $54.70  
  Purchase #6 $71.75   5.327%   $75.5721   $75.57   $75.55   $75.60  
  Purchase #7 $114.37   9.220%   $124.9149   $124.91   $124.90   $124.90  
  7 purchase totals = $745.61       $806.2621   $806.26   $806.30   $806.30