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 $58.92   5.416%   $62.1111   $62.11   $62.10   $62.10  
  Purchase #2 $210.39   13.294%   $238.3592   $238.36   $238.35   $238.40  
  Purchase #3 $194.45   8.795%   $211.5519   $211.55   $211.55   $211.60  
  Purchase #4 $20.52   10.676%   $22.7107   $22.71   $22.70   $22.70  
  Purchase #5 $207.39   3.523%   $214.6963   $214.70   $214.70   $214.70  
  Purchase #6 $73.32   6.811%   $78.3138   $78.31   $78.30   $78.30  
  Purchase #7 $194.90   6.334%   $207.245   $207.25   $207.25   $207.20  
  7 purchase totals = $959.89       $1,034.9880   $1,034.99   $1,034.95   $1,035.00