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 $235.36   10.874%   $260.953   $260.95   $260.95   $261.00  
  Purchase #2 $206.35   4.157%   $214.928   $214.93   $214.95   $214.90  
  Purchase #3 $241.73   8.731%   $262.8354   $262.84   $262.85   $262.80  
  Purchase #4 $244.39   13.365%   $277.0527   $277.05   $277.05   $277.10  
  Purchase #5 $203.34   8.435%   $220.4917   $220.49   $220.50   $220.50  
  Purchase #6 $74.28   13.841%   $84.5611   $84.56   $84.55   $84.60  
  Purchase #7 $163.44   13.700%   $185.8313   $185.83   $185.85   $185.80  
  7 purchase totals = $1,368.89       $1,506.6532   $1,506.65   $1,506.70   $1,506.70