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 $219.28   6.122%   $232.7043   $232.70   $232.70   $232.70  
  Purchase #2 $67.89   13.303%   $76.9214   $76.92   $76.90   $76.90  
  Purchase #3 $164.60   13.439%   $186.7206   $186.72   $186.70   $186.70  
  Purchase #4 $49.51   5.135%   $52.0523   $52.05   $52.05   $52.10  
  Purchase #5 $158.48   3.581%   $164.1552   $164.16   $164.15   $164.20  
  Purchase #6 $8.41   7.134%   $9.01   $9.01   $9.00   $9.00  
  Purchase #7 $211.68   12.806%   $238.7877   $238.79   $238.80   $238.80  
  7 purchase totals = $879.85       $960.3515   $960.35   $960.30   $960.40