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 $89.51   3.394%   $92.548   $92.55   $92.55   $92.50  
  Purchase #2 $13.52   7.264%   $14.5021   $14.50   $14.50   $14.50  
  Purchase #3 $212.64   5.245%   $223.793   $223.79   $223.80   $223.80  
  Purchase #4 $87.83   10.474%   $97.0293   $97.03   $97.05   $97.00  
  Purchase #5 $248.71   7.708%   $267.8806   $267.88   $267.90   $267.90  
  Purchase #6 $250.80   5.686%   $265.0605   $265.06   $265.05   $265.10  
  Purchase #7 $127.93   4.822%   $134.0988   $134.10   $134.10   $134.10  
  7 purchase totals = $1,030.94       $1,094.9123   $1,094.91   $1,094.95   $1,094.90