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 $186.95   5.156%   $196.5891   $196.59   $196.60   $196.60  
  Purchase #2 $220.82   7.577%   $237.5515   $237.55   $237.55   $237.60  
  Purchase #3 $241.60   5.289%   $254.3782   $254.38   $254.40   $254.40  
  Purchase #4 $237.28   9.199%   $259.1074   $259.11   $259.10   $259.10  
  Purchase #5 $98.81   3.270%   $102.0411   $102.04   $102.05   $102.00  
  Purchase #6 $235.96   12.540%   $265.5494   $265.55   $265.55   $265.50  
  Purchase #7 $177.30   5.473%   $187.0036   $187.00   $187.00   $187.00  
  7 purchase totals = $1,398.72       $1,502.2203   $1,502.22   $1,502.25   $1,502.20