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 $61.28   10.447%   $67.6819   $67.68   $67.70   $67.70  
  Purchase #2 $65.79   4.411%   $68.692   $68.69   $68.70   $68.70  
  Purchase #3 $181.56   11.521%   $202.4775   $202.48   $202.50   $202.50  
  Purchase #4 $246.96   8.588%   $268.1689   $268.17   $268.15   $268.20  
  Purchase #5 $119.27   11.834%   $133.3844   $133.38   $133.40   $133.40  
  Purchase #6 $222.60   12.625%   $250.7033   $250.70   $250.70   $250.70  
  Purchase #7 $30.80   12.179%   $34.5511   $34.55   $34.55   $34.60  
  7 purchase totals = $928.26       $1,025.6591   $1,025.65   $1,025.70   $1,025.80