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 $184.72   4.679%   $193.363   $193.36   $193.35   $193.40  
  Purchase #2 $206.66   4.789%   $216.5569   $216.56   $216.55   $216.60  
  Purchase #3 $125.72   6.703%   $134.147   $134.15   $134.15   $134.10  
  Purchase #4 $65.54   11.508%   $73.0823   $73.08   $73.10   $73.10  
  Purchase #5 $211.31   5.546%   $223.0293   $223.03   $223.05   $223.00  
  Purchase #6 $105.50   4.181%   $109.911   $109.91   $109.90   $109.90  
  Purchase #7 $58.77   8.182%   $63.5786   $63.58   $63.60   $63.60  
  7 purchase totals = $958.22       $1,013.6681   $1,013.67   $1,013.70   $1,013.70