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 $88.66   7.706%   $95.4921   $95.49   $95.50   $95.50  
  Purchase #2 $22.82   7.244%   $24.4731   $24.47   $24.45   $24.50  
  Purchase #3 $83.62   11.510%   $93.2447   $93.24   $93.25   $93.20  
  Purchase #4 $181.54   7.774%   $195.6529   $195.65   $195.65   $195.70  
  Purchase #5 $213.60   13.298%   $242.0045   $242.00   $242.00   $242.00  
  Purchase #6 $176.73   13.233%   $200.1167   $200.12   $200.10   $200.10  
  Purchase #7 $236.55   5.720%   $250.0807   $250.08   $250.10   $250.10  
  7 purchase totals = $1,003.52       $1,101.0647   $1,101.05   $1,101.05   $1,101.10