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 $134.77   9.862%   $148.061   $148.06   $148.05   $148.10  
  Purchase #2 $189.98   11.529%   $211.8828   $211.88   $211.90   $211.90  
  Purchase #3 $41.71   10.403%   $46.0491   $46.05   $46.05   $46.00  
  Purchase #4 $240.72   10.823%   $266.7731   $266.77   $266.75   $266.80  
  Purchase #5 $245.46   7.181%   $263.0865   $263.09   $263.10   $263.10  
  Purchase #6 $22.65   6.325%   $24.0826   $24.08   $24.10   $24.10  
  Purchase #7 $227.69   12.682%   $256.5656   $256.57   $256.55   $256.60  
  7 purchase totals = $1,102.98       $1,216.5007   $1,216.50   $1,216.50   $1,216.60