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 $87.83   5.480%   $92.6431   $92.64   $92.65   $92.60  
  Purchase #2 $180.61   5.718%   $190.9373   $190.94   $190.95   $190.90  
  Purchase #3 $76.99   11.341%   $85.7214   $85.72   $85.70   $85.70  
  Purchase #4 $9.44   11.441%   $10.52   $10.52   $10.50   $10.50  
  Purchase #5 $39.39   6.499%   $41.95   $41.95   $41.95   $42.00  
  Purchase #6 $236.66   11.796%   $264.5764   $264.58   $264.60   $264.60  
  Purchase #7 $214.39   3.419%   $221.72   $221.72   $221.70   $221.70  
  7 purchase totals = $845.31       $908.0682   $908.07   $908.05   $908.00