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 $196.32   5.790%   $207.6869   $207.69   $207.70   $207.70  
  Purchase #2 $209.27   12.581%   $235.5983   $235.60   $235.60   $235.60  
  Purchase #3 $74.29   7.304%   $79.7161   $79.72   $79.70   $79.70  
  Purchase #4 $54.61   12.391%   $61.3767   $61.38   $61.40   $61.40  
  Purchase #5 $107.82   10.671%   $119.3255   $119.33   $119.35   $119.30  
  Purchase #6 $117.86   4.125%   $122.7217   $122.72   $122.70   $122.70  
  Purchase #7 $24.46   7.156%   $26.2104   $26.21   $26.20   $26.20  
  7 purchase totals = $784.63       $852.6356   $852.65   $852.65   $852.60