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 $167.95   10.518%   $185.615   $185.62   $185.60   $185.60  
  Purchase #2 $250.43   6.870%   $267.6345   $267.63   $267.65   $267.60  
  Purchase #3 $92.73   6.495%   $98.7528   $98.75   $98.75   $98.80  
  Purchase #4 $67.49   4.490%   $70.5203   $70.52   $70.50   $70.50  
  Purchase #5 $24.69   8.713%   $26.8412   $26.84   $26.85   $26.80  
  Purchase #6 $74.31   3.718%   $77.0728   $77.07   $77.05   $77.10  
  Purchase #7 $205.61   8.613%   $223.3192   $223.32   $223.30   $223.30  
  7 purchase totals = $883.21       $949.7558   $949.75   $949.70   $949.70