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 $83.85   12.849%   $94.6239   $94.62   $94.60   $94.60  
  Purchase #2 $128.31   9.302%   $140.2454   $140.25   $140.25   $140.20  
  Purchase #3 $13.49   12.547%   $15.1826   $15.18   $15.20   $15.20  
  Purchase #4 $223.79   12.395%   $251.5288   $251.53   $251.55   $251.50  
  Purchase #5 $166.68   10.170%   $183.6314   $183.63   $183.65   $183.60  
  Purchase #6 $226.48   4.515%   $236.7056   $236.71   $236.70   $236.70  
  Purchase #7 $195.33   3.757%   $202.6685   $202.67   $202.65   $202.70  
  7 purchase totals = $1,037.93       $1,124.5862   $1,124.59   $1,124.60   $1,124.50