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 $44.84   8.651%   $48.7191   $48.72   $48.70   $48.70  
  Purchase #2 $23.96   8.348%   $25.9602   $25.96   $25.95   $26.00  
  Purchase #3 $82.64   13.370%   $93.689   $93.69   $93.70   $93.70  
  Purchase #4 $234.49   13.718%   $266.6573   $266.66   $266.65   $266.70  
  Purchase #5 $58.40   3.684%   $60.5515   $60.55   $60.55   $60.60  
  Purchase #6 $161.88   7.180%   $173.503   $173.50   $173.50   $173.50  
  Purchase #7 $71.28   10.107%   $78.4843   $78.48   $78.50   $78.50  
  7 purchase totals = $677.49       $747.5644   $747.56   $747.55   $747.70