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 $87.26   6.631%   $93.0462   $93.05   $93.05   $93.00  
  Purchase #2 $187.80   4.724%   $196.6717   $196.67   $196.65   $196.70  
  Purchase #3 $39.53   8.814%   $43.0142   $43.01   $43.00   $43.00  
  Purchase #4 $46.95   6.588%   $50.0431   $50.04   $50.05   $50.00  
  Purchase #5 $224.36   4.583%   $234.6424   $234.64   $234.65   $234.60  
  Purchase #6 $195.67   8.497%   $212.2961   $212.30   $212.30   $212.30  
  Purchase #7 $215.80   3.849%   $224.1061   $224.11   $224.10   $224.10  
  7 purchase totals = $997.37       $1,053.8198   $1,053.82   $1,053.80   $1,053.70