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 $160.89   4.798%   $168.6095   $168.61   $168.60   $168.60  
  Purchase #2 $214.31   8.721%   $233   $233.00   $233.00   $233.00  
  Purchase #3 $139.68   10.777%   $154.7333   $154.73   $154.75   $154.70  
  Purchase #4 $156.77   4.798%   $164.2918   $164.29   $164.30   $164.30  
  Purchase #5 $192.89   4.471%   $201.5141   $201.51   $201.50   $201.50  
  Purchase #6 $232.65   4.700%   $243.5846   $243.58   $243.60   $243.60  
  Purchase #7 $230.34   8.658%   $250.2828   $250.28   $250.30   $250.30  
  7 purchase totals = $1,327.53       $1,416.0161   $1,416.00   $1,416.05   $1,416.00