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 $147.57   7.110%   $158.0622   $158.06   $158.05   $158.10  
  Purchase #2 $68.96   5.411%   $72.6914   $72.69   $72.70   $72.70  
  Purchase #3 $158.26   11.157%   $175.9171   $175.92   $175.90   $175.90  
  Purchase #4 $215.59   12.529%   $242.6013   $242.60   $242.60   $242.60  
  Purchase #5 $96.93   11.374%   $107.9548   $107.95   $107.95   $108.00  
  Purchase #6 $216.54   13.149%   $245.0128   $245.01   $245.00   $245.00  
  Purchase #7 $50.65   10.433%   $55.9343   $55.93   $55.95   $55.90  
  7 purchase totals = $954.50       $1,058.1739   $1,058.16   $1,058.15   $1,058.20