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 $62.92   3.362%   $65.0354   $65.04   $65.05   $65.00  
  Purchase #2 $187.49   7.646%   $201.8255   $201.83   $201.85   $201.80  
  Purchase #3 $106.89   13.856%   $121.7007   $121.70   $121.70   $121.70  
  Purchase #4 $212.80   13.596%   $241.7323   $241.73   $241.75   $241.70  
  Purchase #5 $207.85   11.166%   $231.0585   $231.06   $231.05   $231.10  
  Purchase #6 $157.34   6.651%   $167.8047   $167.80   $167.80   $167.80  
  Purchase #7 $192.53   12.439%   $216.4788   $216.48   $216.50   $216.50  
  7 purchase totals = $1,127.82       $1,245.6359   $1,245.64   $1,245.70   $1,245.60