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 $86.96   7.637%   $93.6011   $93.60   $93.60   $93.60  
  Purchase #2 $63.46   7.207%   $68.0336   $68.03   $68.05   $68.00  
  Purchase #3 $93.36   10.784%   $103.4279   $103.43   $103.45   $103.40  
  Purchase #4 $121.91   7.417%   $130.9521   $130.95   $130.95   $131.00  
  Purchase #5 $203.36   10.297%   $224.3   $224.30   $224.30   $224.30  
  Purchase #6 $248.61   5.653%   $262.6639   $262.66   $262.65   $262.70  
  Purchase #7 $151.82   8.822%   $165.2136   $165.21   $165.20   $165.20  
  7 purchase totals = $969.48       $1,048.1922   $1,048.18   $1,048.20   $1,048.20