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 $95.31   10.759%   $105.5644   $105.56   $105.55   $105.60  
  Purchase #2 $186.73   6.642%   $199.1326   $199.13   $199.15   $199.10  
  Purchase #3 $222.30   9.416%   $243.2318   $243.23   $243.25   $243.20  
  Purchase #4 $165.28   6.809%   $176.5339   $176.53   $176.55   $176.50  
  Purchase #5 $24.67   9.784%   $27.0837   $27.08   $27.10   $27.10  
  Purchase #6 $236.26   3.866%   $245.3938   $245.39   $245.40   $245.40  
  Purchase #7 $28.55   3.291%   $29.4896   $29.49   $29.50   $29.50  
  7 purchase totals = $959.10       $1,026.4298   $1,026.41   $1,026.50   $1,026.40