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 $58.65   7.584%   $63.098   $63.10   $63.10   $63.10  
  Purchase #2 $93.51   6.728%   $99.8014   $99.80   $99.80   $99.80  
  Purchase #3 $135.81   4.539%   $141.9744   $141.97   $141.95   $142.00  
  Purchase #4 $238.59   7.820%   $257.2477   $257.25   $257.25   $257.20  
  Purchase #5 $61.61   11.615%   $68.766   $68.77   $68.75   $68.80  
  Purchase #6 $242.66   9.629%   $266.0257   $266.03   $266.05   $266.00  
  Purchase #7 $190.65   4.800%   $199.8012   $199.80   $199.80   $199.80  
  7 purchase totals = $1,021.48       $1,096.7144   $1,096.72   $1,096.70   $1,096.70