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 $239.59   9.793%   $263.053   $263.05   $263.05   $263.10  
  Purchase #2 $231.86   9.668%   $254.2762   $254.28   $254.30   $254.30  
  Purchase #3 $96.39   7.587%   $103.7031   $103.70   $103.70   $103.70  
  Purchase #4 $155.41   10.691%   $172.0249   $172.02   $172.00   $172.00  
  Purchase #5 $114.35   12.629%   $128.7913   $128.79   $128.80   $128.80  
  Purchase #6 $14.28   13.870%   $16.2606   $16.26   $16.25   $16.30  
  Purchase #7 $198.72   13.690%   $225.9248   $225.92   $225.90   $225.90  
  7 purchase totals = $1,050.60       $1,164.0339   $1,164.02   $1,164.00   $1,164.10