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 $215.29   13.583%   $244.5328   $244.53   $244.55   $244.50  
  Purchase #2 $246.29   4.458%   $257.2696   $257.27   $257.25   $257.30  
  Purchase #3 $68.34   9.298%   $74.6943   $74.69   $74.70   $74.70  
  Purchase #4 $20.45   13.687%   $23.249   $23.25   $23.25   $23.20  
  Purchase #5 $136.69   9.133%   $149.1739   $149.17   $149.15   $149.20  
  Purchase #6 $201.49   4.162%   $209.876   $209.88   $209.90   $209.90  
  Purchase #7 $206.92   7.182%   $221.781   $221.78   $221.80   $221.80  
  7 purchase totals = $1,095.47       $1,180.5766   $1,180.57   $1,180.60   $1,180.60