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 $86.31   10.222%   $95.1326   $95.13   $95.15   $95.10  
  Purchase #2 $114.80   13.576%   $130.3852   $130.39   $130.40   $130.40  
  Purchase #3 $179.59   13.871%   $204.5009   $204.50   $204.50   $204.50  
  Purchase #4 $125.29   5.861%   $132.6332   $132.63   $132.65   $132.60  
  Purchase #5 $78.45   3.675%   $81.333   $81.33   $81.35   $81.30  
  Purchase #6 $199.86   13.317%   $226.4754   $226.48   $226.50   $226.50  
  Purchase #7 $193.31   4.354%   $201.7267   $201.73   $201.75   $201.70  
  7 purchase totals = $977.61       $1,072.1870   $1,072.19   $1,072.30   $1,072.10