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 $180.85   8.572%   $196.3525   $196.35   $196.35   $196.40  
  Purchase #2 $113.55   8.218%   $122.8815   $122.88   $122.90   $122.90  
  Purchase #3 $45.71   3.527%   $47.3222   $47.32   $47.30   $47.30  
  Purchase #4 $113.36   12.342%   $127.3509   $127.35   $127.35   $127.40  
  Purchase #5 $166.32   6.667%   $177.4086   $177.41   $177.40   $177.40  
  Purchase #6 $248.59   6.200%   $264.0026   $264.00   $264.00   $264.00  
  Purchase #7 $153.70   4.684%   $160.8993   $160.90   $160.90   $160.90  
  7 purchase totals = $1,022.08       $1,096.2176   $1,096.21   $1,096.20   $1,096.30