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 $183.41   7.326%   $196.8466   $196.85   $196.85   $196.80  
  Purchase #2 $40.68   3.251%   $42.0025   $42.00   $42.00   $42.00  
  Purchase #3 $177.27   13.706%   $201.5666   $201.57   $201.55   $201.60  
  Purchase #4 $91.30   3.440%   $94.4407   $94.44   $94.45   $94.40  
  Purchase #5 $245.44   3.248%   $253.4119   $253.41   $253.40   $253.40  
  Purchase #6 $234.78   7.644%   $252.7266   $252.73   $252.75   $252.70  
  Purchase #7 $68.36   3.577%   $70.8052   $70.81   $70.80   $70.80  
  7 purchase totals = $1,041.24       $1,111.8001   $1,111.81   $1,111.80   $1,111.70