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 $111.42   13.568%   $126.5375   $126.54   $126.55   $126.50  
  Purchase #2 $206.84   8.671%   $224.7751   $224.78   $224.80   $224.80  
  Purchase #3 $39.67   12.585%   $44.6625   $44.66   $44.65   $44.70  
  Purchase #4 $236.53   7.530%   $254.3407   $254.34   $254.35   $254.30  
  Purchase #5 $190.25   10.732%   $210.6676   $210.67   $210.65   $210.70  
  Purchase #6 $116.62   12.721%   $131.4552   $131.46   $131.45   $131.50  
  Purchase #7 $201.43   4.343%   $210.1781   $210.18   $210.20   $210.20  
  7 purchase totals = $1,102.76       $1,202.6167   $1,202.63   $1,202.65   $1,202.70