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 $167.64   10.282%   $184.8767   $184.88   $184.90   $184.90  
  Purchase #2 $182.38   10.378%   $201.3074   $201.31   $201.30   $201.30  
  Purchase #3 $209.53   5.649%   $221.3663   $221.37   $221.35   $221.40  
  Purchase #4 $26.90   10.346%   $29.6831   $29.68   $29.70   $29.70  
  Purchase #5 $206.73   8.615%   $224.5398   $224.54   $224.55   $224.50  
  Purchase #6 $186.88   11.253%   $207.9096   $207.91   $207.90   $207.90  
  Purchase #7 $34.62   8.213%   $37.4633   $37.46   $37.45   $37.50  
  7 purchase totals = $1,014.68       $1,107.1462   $1,107.15   $1,107.15   $1,107.20