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 $58.80   4.216%   $61.279   $61.28   $61.30   $61.30  
  Purchase #2 $247.54   3.544%   $256.3128   $256.31   $256.30   $256.30  
  Purchase #3 $166.48   8.307%   $180.3095   $180.31   $180.30   $180.30  
  Purchase #4 $118.65   12.477%   $133.454   $133.45   $133.45   $133.50  
  Purchase #5 $197.30   11.758%   $220.4985   $220.50   $220.50   $220.50  
  Purchase #6 $61.51   5.141%   $64.6722   $64.67   $64.65   $64.70  
  Purchase #7 $177.35   4.804%   $185.8699   $185.87   $185.85   $185.90  
  7 purchase totals = $1,027.63       $1,102.3959   $1,102.39   $1,102.35   $1,102.50