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 $201.60   11.110%   $223.9978   $224.00   $224.00   $224.00  
  Purchase #2 $48.49   6.665%   $51.7219   $51.72   $51.70   $51.70  
  Purchase #3 $212.92   5.285%   $224.1728   $224.17   $224.15   $224.20  
  Purchase #4 $250.89   7.488%   $269.6766   $269.68   $269.70   $269.70  
  Purchase #5 $209.99   5.668%   $221.8922   $221.89   $221.90   $221.90  
  Purchase #6 $20.66   10.538%   $22.8372   $22.84   $22.85   $22.80  
  Purchase #7 $150.26   7.290%   $161.214   $161.21   $161.20   $161.20  
  7 purchase totals = $1,094.81       $1,175.5125   $1,175.51   $1,175.50   $1,175.50