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 $86.65   5.711%   $91.5986   $91.60   $91.60   $91.60  
  Purchase #2 $174.47   13.664%   $198.3096   $198.31   $198.30   $198.30  
  Purchase #3 $65.73   12.214%   $73.7583   $73.76   $73.75   $73.80  
  Purchase #4 $212.52   5.218%   $223.6093   $223.61   $223.60   $223.60  
  Purchase #5 $76.72   3.836%   $79.663   $79.66   $79.65   $79.70  
  Purchase #6 $240.70   10.706%   $266.4693   $266.47   $266.45   $266.50  
  Purchase #7 $85.44   9.356%   $93.4338   $93.43   $93.45   $93.40  
  7 purchase totals = $942.23       $1,026.8419   $1,026.84   $1,026.80   $1,026.90