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 $118.26   4.615%   $123.7177   $123.72   $123.70   $123.70  
  Purchase #2 $183.74   10.327%   $202.7148   $202.71   $202.70   $202.70  
  Purchase #3 $157.48   12.468%   $177.1146   $177.11   $177.10   $177.10  
  Purchase #4 $60.27   11.645%   $67.2884   $67.29   $67.30   $67.30  
  Purchase #5 $111.87   6.871%   $119.5566   $119.56   $119.55   $119.60  
  Purchase #6 $37.66   12.356%   $42.3133   $42.31   $42.30   $42.30  
  Purchase #7 $26.30   4.372%   $27.4498   $27.45   $27.45   $27.40  
  7 purchase totals = $695.58       $760.1552   $760.15   $760.10   $760.10