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 $210.71   7.615%   $226.7556   $226.76   $226.75   $226.80  
  Purchase #2 $62.95   9.618%   $69.0045   $69.00   $69.00   $69.00  
  Purchase #3 $193.62   4.367%   $202.0754   $202.08   $202.10   $202.10  
  Purchase #4 $167.81   10.485%   $185.4049   $185.40   $185.40   $185.40  
  Purchase #5 $161.36   6.183%   $171.3369   $171.34   $171.35   $171.30  
  Purchase #6 $151.28   4.211%   $157.6504   $157.65   $157.65   $157.70  
  Purchase #7 $238.31   5.563%   $251.5672   $251.57   $251.55   $251.60  
  7 purchase totals = $1,186.04       $1,263.7949   $1,263.80   $1,263.80   $1,263.90