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 $201.99   5.228%   $212.55   $212.55   $212.55   $212.60  
  Purchase #2 $41.67   4.472%   $43.5335   $43.53   $43.55   $43.50  
  Purchase #3 $21.53   5.218%   $22.6534   $22.65   $22.65   $22.70  
  Purchase #4 $157.28   7.481%   $169.0461   $169.05   $169.05   $169.00  
  Purchase #5 $146.43   10.355%   $161.5928   $161.59   $161.60   $161.60  
  Purchase #6 $237.28   10.379%   $261.9073   $261.91   $261.90   $261.90  
  Purchase #7 $207.55   6.603%   $221.2545   $221.25   $221.25   $221.30  
  7 purchase totals = $1,013.73       $1,092.5376   $1,092.53   $1,092.55   $1,092.60