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 $98.61   7.182%   $105.6922   $105.69   $105.70   $105.70  
  Purchase #2 $211.34   4.713%   $221.3005   $221.30   $221.30   $221.30  
  Purchase #3 $29.76   7.503%   $31.9929   $31.99   $32.00   $32.00  
  Purchase #4 $6.68   6.187%   $7.0933   $7.09   $7.10   $7.10  
  Purchase #5 $227.49   10.802%   $252.0635   $252.06   $252.05   $252.10  
  Purchase #6 $149.63   12.110%   $167.7502   $167.75   $167.75   $167.80  
  Purchase #7 $201.45   13.237%   $228.1159   $228.12   $228.10   $228.10  
  7 purchase totals = $924.96       $1,014.0085   $1,014.00   $1,014.00   $1,014.10