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 $83.92   11.655%   $93.7009   $93.70   $93.70   $93.70  
  Purchase #2 $104.84   12.644%   $118.096   $118.10   $118.10   $118.10  
  Purchase #3 $162.59   4.747%   $170.3081   $170.31   $170.30   $170.30  
  Purchase #4 $249.34   13.312%   $282.5321   $282.53   $282.55   $282.50  
  Purchase #5 $164.35   6.195%   $174.5315   $174.53   $174.55   $174.50  
  Purchase #6 $217.39   10.270%   $239.716   $239.72   $239.70   $239.70  
  Purchase #7 $25.28   5.185%   $26.5908   $26.59   $26.60   $26.60  
  7 purchase totals = $1,007.71       $1,105.4754   $1,105.48   $1,105.50   $1,105.40