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 $196.65   8.151%   $212.6789   $212.68   $212.70   $212.70  
  Purchase #2 $8.27   7.758%   $8.9116   $8.91   $8.90   $8.90  
  Purchase #3 $83.68   4.695%   $87.6088   $87.61   $87.60   $87.60  
  Purchase #4 $219.85   6.690%   $234.558   $234.56   $234.55   $234.60  
  Purchase #5 $225.41   10.348%   $248.7354   $248.74   $248.75   $248.70  
  Purchase #6 $116.72   11.518%   $130.1638   $130.16   $130.15   $130.20  
  Purchase #7 $128.40   8.761%   $139.6491   $139.65   $139.65   $139.60  
  7 purchase totals = $978.98       $1,062.3056   $1,062.31   $1,062.30   $1,062.30