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 $118.43   6.408%   $126.019   $126.02   $126.00   $126.00  
  Purchase #2 $245.65   5.416%   $258.9544   $258.95   $258.95   $259.00  
  Purchase #3 $140.40   10.183%   $154.6969   $154.70   $154.70   $154.70  
  Purchase #4 $239.79   10.169%   $264.1742   $264.17   $264.15   $264.20  
  Purchase #5 $132.71   6.478%   $141.307   $141.31   $141.30   $141.30  
  Purchase #6 $137.56   3.827%   $142.8244   $142.82   $142.80   $142.80  
  Purchase #7 $182.84   13.258%   $207.0809   $207.08   $207.10   $207.10  
  7 purchase totals = $1,197.38       $1,295.0568   $1,295.05   $1,295.00   $1,295.10