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 $184.43   6.273%   $195.9993   $196.00   $196.00   $196.00  
  Purchase #2 $152.91   8.327%   $165.6428   $165.64   $165.65   $165.60  
  Purchase #3 $169.81   4.143%   $176.8452   $176.85   $176.85   $176.80  
  Purchase #4 $36.82   3.663%   $38.1687   $38.17   $38.15   $38.20  
  Purchase #5 $162.80   3.177%   $167.9722   $167.97   $167.95   $168.00  
  Purchase #6 $232.78   10.677%   $257.6339   $257.63   $257.65   $257.60  
  Purchase #7 $50.28   5.571%   $53.0811   $53.08   $53.10   $53.10  
  7 purchase totals = $989.83       $1,055.3432   $1,055.34   $1,055.35   $1,055.30