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 $98.73   12.381%   $110.9538   $110.95   $110.95   $111.00  
  Purchase #2 $161.86   8.649%   $175.8593   $175.86   $175.85   $175.90  
  Purchase #3 $128.37   5.177%   $135.0157   $135.02   $135.00   $135.00  
  Purchase #4 $43.39   5.856%   $45.9309   $45.93   $45.95   $45.90  
  Purchase #5 $21.68   4.565%   $22.6697   $22.67   $22.65   $22.70  
  Purchase #6 $204.44   11.594%   $228.1428   $228.14   $228.15   $228.10  
  Purchase #7 $220.66   5.601%   $233.0192   $233.02   $233.00   $233.00  
  7 purchase totals = $879.13       $951.5914   $951.59   $951.55   $951.60