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 $118.99   5.668%   $125.7344   $125.73   $125.75   $125.70  
  Purchase #2 $113.65   9.184%   $124.0876   $124.09   $124.10   $124.10  
  Purchase #3 $159.48   12.583%   $179.5474   $179.55   $179.55   $179.50  
  Purchase #4 $247.54   6.409%   $263.4048   $263.40   $263.40   $263.40  
  Purchase #5 $10.80   9.177%   $11.7911   $11.79   $11.80   $11.80  
  Purchase #6 $181.97   4.401%   $189.9785   $189.98   $190.00   $190.00  
  Purchase #7 $114.66   12.313%   $128.7781   $128.78   $128.80   $128.80  
  7 purchase totals = $947.09       $1,023.3219   $1,023.32   $1,023.40   $1,023.30