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 $178.95   8.240%   $193.6955   $193.70   $193.70   $193.70  
  Purchase #2 $162.39   11.758%   $181.4838   $181.48   $181.50   $181.50  
  Purchase #3 $53.29   10.107%   $58.676   $58.68   $58.70   $58.70  
  Purchase #4 $249.46   3.685%   $258.6526   $258.65   $258.65   $258.70  
  Purchase #5 $42.69   8.602%   $46.3622   $46.36   $46.35   $46.40  
  Purchase #6 $176.52   12.857%   $199.2152   $199.22   $199.20   $199.20  
  Purchase #7 $103.76   11.782%   $115.985   $115.99   $116.00   $116.00  
  7 purchase totals = $967.06       $1,054.0703   $1,054.08   $1,054.10   $1,054.20