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 $42.69   7.864%   $46.0471   $46.05   $46.05   $46.00  
  Purchase #2 $198.79   3.617%   $205.9802   $205.98   $206.00   $206.00  
  Purchase #3 $79.32   7.849%   $85.5458   $85.55   $85.55   $85.50  
  Purchase #4 $168.95   4.197%   $176.0408   $176.04   $176.05   $176.00  
  Purchase #5 $30.71   12.737%   $34.6215   $34.62   $34.60   $34.60  
  Purchase #6 $66.96   9.798%   $73.5207   $73.52   $73.50   $73.50  
  Purchase #7 $153.96   7.363%   $165.2961   $165.30   $165.30   $165.30  
  7 purchase totals = $741.38       $787.0522   $787.06   $787.05   $786.90