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 $92.27   5.767%   $97.5912   $97.59   $97.60   $97.60  
  Purchase #2 $225.30   6.489%   $239.9197   $239.92   $239.90   $239.90  
  Purchase #3 $171.54   6.649%   $182.9457   $182.95   $182.95   $182.90  
  Purchase #4 $78.93   8.728%   $85.819   $85.82   $85.80   $85.80  
  Purchase #5 $92.36   4.303%   $96.3343   $96.33   $96.35   $96.30  
  Purchase #6 $245.62   8.765%   $267.1486   $267.15   $267.15   $267.10  
  Purchase #7 $87.72   8.639%   $95.2981   $95.30   $95.30   $95.30  
  7 purchase totals = $993.74       $1,065.0566   $1,065.06   $1,065.05   $1,064.90