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 $41.98   11.774%   $46.9227   $46.92   $46.90   $46.90  
  Purchase #2 $166.32   4.828%   $174.3499   $174.35   $174.35   $174.30  
  Purchase #3 $244.92   12.814%   $276.304   $276.30   $276.30   $276.30  
  Purchase #4 $168.73   3.470%   $174.5849   $174.58   $174.60   $174.60  
  Purchase #5 $118.89   12.625%   $133.8999   $133.90   $133.90   $133.90  
  Purchase #6 $243.69   3.500%   $252.2192   $252.22   $252.20   $252.20  
  Purchase #7 $209.67   11.617%   $234.0274   $234.03   $234.05   $234.00  
  7 purchase totals = $1,194.20       $1,292.3080   $1,292.30   $1,292.30   $1,292.20