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 $193.69   3.794%   $201.0386   $201.04   $201.05   $201.00  
  Purchase #2 $194.50   9.120%   $212.2384   $212.24   $212.25   $212.20  
  Purchase #3 $123.30   8.224%   $133.4402   $133.44   $133.45   $133.40  
  Purchase #4 $65.44   4.216%   $68.199   $68.20   $68.20   $68.20  
  Purchase #5 $107.78   8.579%   $117.0264   $117.03   $117.05   $117.00  
  Purchase #6 $187.49   5.655%   $198.0926   $198.09   $198.10   $198.10  
  Purchase #7 $56.52   13.275%   $64.023   $64.02   $64.00   $64.00  
  7 purchase totals = $928.72       $994.0582   $994.06   $994.10   $993.90