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 $35.77   6.276%   $38.0149   $38.01   $38.00   $38.00  
  Purchase #2 $227.36   3.675%   $235.7155   $235.72   $235.70   $235.70  
  Purchase #3 $179.48   3.688%   $186.0992   $186.10   $186.10   $186.10  
  Purchase #4 $48.58   5.869%   $51.4312   $51.43   $51.45   $51.40  
  Purchase #5 $183.86   6.769%   $196.3055   $196.31   $196.30   $196.30  
  Purchase #6 $97.51   9.588%   $106.8593   $106.86   $106.85   $106.90  
  Purchase #7 $224.61   9.571%   $246.1074   $246.11   $246.10   $246.10  
  7 purchase totals = $997.17       $1,060.5330   $1,060.54   $1,060.50   $1,060.50