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 $181.82   11.182%   $202.1511   $202.15   $202.15   $202.20  
  Purchase #2 $117.97   3.397%   $121.9774   $121.98   $122.00   $122.00  
  Purchase #3 $36.43   7.274%   $39.0799   $39.08   $39.10   $39.10  
  Purchase #4 $154.97   7.685%   $166.8794   $166.88   $166.90   $166.90  
  Purchase #5 $181.41   9.193%   $198.087   $198.09   $198.10   $198.10  
  Purchase #6 $50.31   5.626%   $53.1404   $53.14   $53.15   $53.10  
  Purchase #7 $94.71   12.598%   $106.6416   $106.64   $106.65   $106.60  
  7 purchase totals = $817.62       $887.9568   $887.96   $888.05   $888.00