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 $215.69   8.495%   $234.0129   $234.01   $234.00   $234.00  
  Purchase #2 $176.36   10.750%   $195.3187   $195.32   $195.30   $195.30  
  Purchase #3 $106.40   9.590%   $116.6038   $116.60   $116.60   $116.60  
  Purchase #4 $94.73   11.670%   $105.785   $105.79   $105.80   $105.80  
  Purchase #5 $167.47   10.605%   $185.2302   $185.23   $185.25   $185.20  
  Purchase #6 $188.58   10.219%   $207.851   $207.85   $207.85   $207.90  
  Purchase #7 $167.45   4.261%   $174.585   $174.59   $174.60   $174.60  
  7 purchase totals = $1,116.68       $1,219.3866   $1,219.39   $1,219.40   $1,219.40