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 $215.49   5.283%   $226.8743   $226.87   $226.85   $226.90  
  Purchase #2 $90.67   6.431%   $96.501   $96.50   $96.50   $96.50  
  Purchase #3 $200.71   6.610%   $213.9769   $213.98   $214.00   $214.00  
  Purchase #4 $75.37   6.721%   $80.4356   $80.44   $80.45   $80.40  
  Purchase #5 $60.41   3.506%   $62.528   $62.53   $62.55   $62.50  
  Purchase #6 $105.44   13.625%   $119.8062   $119.81   $119.80   $119.80  
  Purchase #7 $193.30   9.387%   $211.4451   $211.45   $211.45   $211.40  
  7 purchase totals = $941.39       $1,011.5671   $1,011.58   $1,011.60   $1,011.50