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 $191.32   5.832%   $202.4778   $202.48   $202.50   $202.50  
  Purchase #2 $99.55   5.183%   $104.7097   $104.71   $104.70   $104.70  
  Purchase #3 $160.42   5.569%   $169.3538   $169.35   $169.35   $169.40  
  Purchase #4 $177.65   5.800%   $187.9537   $187.95   $187.95   $188.00  
  Purchase #5 $229.68   11.520%   $256.1391   $256.14   $256.15   $256.10  
  Purchase #6 $248.60   6.233%   $264.0952   $264.10   $264.10   $264.10  
  Purchase #7 $46.50   11.392%   $51.7973   $51.80   $51.80   $51.80  
  7 purchase totals = $1,153.72       $1,236.5266   $1,236.53   $1,236.55   $1,236.60