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 $184.41   9.516%   $201.9585   $201.96   $201.95   $202.00  
  Purchase #2 $108.46   8.706%   $117.9025   $117.90   $117.90   $117.90  
  Purchase #3 $196.39   3.819%   $203.8901   $203.89   $203.90   $203.90  
  Purchase #4 $113.27   13.343%   $128.3836   $128.38   $128.40   $128.40  
  Purchase #5 $92.64   13.376%   $105.0315   $105.03   $105.05   $105.00  
  Purchase #6 $247.96   11.280%   $275.9299   $275.93   $275.95   $275.90  
  Purchase #7 $10.71   7.864%   $11.5522   $11.55   $11.55   $11.60  
  7 purchase totals = $953.84       $1,044.6483   $1,044.64   $1,044.70   $1,044.70