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 $168.80   4.572%   $176.5175   $176.52   $176.50   $176.50  
  Purchase #2 $57.76   5.575%   $60.9801   $60.98   $61.00   $61.00  
  Purchase #3 $113.27   5.408%   $119.3956   $119.40   $119.40   $119.40  
  Purchase #4 $67.86   5.570%   $71.6398   $71.64   $71.65   $71.60  
  Purchase #5 $45.26   3.573%   $46.8771   $46.88   $46.90   $46.90  
  Purchase #6 $249.92   4.690%   $261.6412   $261.64   $261.65   $261.60  
  Purchase #7 $9.41   10.316%   $10.3807   $10.38   $10.40   $10.40  
  7 purchase totals = $712.28       $747.4320   $747.44   $747.50   $747.40