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 $192.66   11.438%   $214.6965   $214.70   $214.70   $214.70  
  Purchase #2 $63.40   11.298%   $70.5629   $70.56   $70.55   $70.60  
  Purchase #3 $59.27   13.454%   $67.2442   $67.24   $67.25   $67.20  
  Purchase #4 $248.45   11.208%   $276.2963   $276.30   $276.30   $276.30  
  Purchase #5 $149.42   8.128%   $161.5649   $161.56   $161.55   $161.60  
  Purchase #6 $153.29   7.753%   $165.1746   $165.17   $165.15   $165.20  
  Purchase #7 $77.80   13.834%   $88.5629   $88.56   $88.55   $88.60  
  7 purchase totals = $944.29       $1,044.1023   $1,044.09   $1,044.05   $1,044.20