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 $182.99   11.526%   $204.0814   $204.08   $204.10   $204.10  
  Purchase #2 $187.37   5.368%   $197.428   $197.43   $197.45   $197.40  
  Purchase #3 $25.59   3.862%   $26.5783   $26.58   $26.60   $26.60  
  Purchase #4 $81.30   8.555%   $88.2552   $88.26   $88.25   $88.30  
  Purchase #5 $154.33   9.864%   $169.5531   $169.55   $169.55   $169.60  
  Purchase #6 $160.56   11.732%   $179.3969   $179.40   $179.40   $179.40  
  Purchase #7 $241.92   8.341%   $262.0985   $262.10   $262.10   $262.10  
  7 purchase totals = $1,034.06       $1,127.3914   $1,127.40   $1,127.45   $1,127.50