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 $201.33   10.641%   $222.7535   $222.75   $222.75   $222.80  
  Purchase #2 $158.80   9.342%   $173.6351   $173.64   $173.65   $173.60  
  Purchase #3 $27.57   11.282%   $30.6804   $30.68   $30.70   $30.70  
  Purchase #4 $110.88   12.430%   $124.6624   $124.66   $124.65   $124.70  
  Purchase #5 $10.61   6.826%   $11.3342   $11.33   $11.35   $11.30  
  Purchase #6 $248.56   10.475%   $274.5967   $274.60   $274.60   $274.60  
  Purchase #7 $96.85   10.743%   $107.2546   $107.25   $107.25   $107.30  
  7 purchase totals = $854.60       $944.9169   $944.91   $944.95   $945.00