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 $214.77   7.562%   $231.0109   $231.01   $231.00   $231.00  
  Purchase #2 $233.83   9.438%   $255.8989   $255.90   $255.90   $255.90  
  Purchase #3 $132.63   10.583%   $146.6662   $146.67   $146.65   $146.70  
  Purchase #4 $99.27   13.835%   $113.004   $113.00   $113.00   $113.00  
  Purchase #5 $22.61   11.518%   $25.2142   $25.21   $25.20   $25.20  
  Purchase #6 $53.67   8.663%   $58.3194   $58.32   $58.30   $58.30  
  Purchase #7 $194.44   12.365%   $218.4825   $218.48   $218.50   $218.50  
  7 purchase totals = $951.22       $1,048.5961   $1,048.59   $1,048.55   $1,048.60