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 $52.67   3.396%   $54.4587   $54.46   $54.45   $54.50  
  Purchase #2 $146.55   4.723%   $153.4716   $153.47   $153.45   $153.50  
  Purchase #3 $168.88   4.706%   $176.8275   $176.83   $176.85   $176.80  
  Purchase #4 $87.84   8.365%   $95.1878   $95.19   $95.20   $95.20  
  Purchase #5 $224.67   3.837%   $233.2906   $233.29   $233.30   $233.30  
  Purchase #6 $153.63   13.354%   $174.1458   $174.15   $174.15   $174.10  
  Purchase #7 $199.28   9.257%   $217.7273   $217.73   $217.75   $217.70  
  7 purchase totals = $1,033.52       $1,105.1093   $1,105.12   $1,105.15   $1,105.10