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 $210.43   10.582%   $232.6977   $232.70   $232.70   $232.70  
  Purchase #2 $230.34   5.671%   $243.4026   $243.40   $243.40   $243.40  
  Purchase #3 $107.98   10.790%   $119.631   $119.63   $119.65   $119.60  
  Purchase #4 $208.56   6.616%   $222.3583   $222.36   $222.35   $222.40  
  Purchase #5 $174.51   5.767%   $184.574   $184.57   $184.55   $184.60  
  Purchase #6 $15.88   3.625%   $16.4557   $16.46   $16.45   $16.50  
  Purchase #7 $6.64   11.218%   $7.3849   $7.38   $7.40   $7.40  
  7 purchase totals = $954.34       $1,026.5042   $1,026.50   $1,026.50   $1,026.60