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 $181.67   8.603%   $197.2991   $197.30   $197.30   $197.30  
  Purchase #2 $228.79   11.720%   $255.6042   $255.60   $255.60   $255.60  
  Purchase #3 $236.99   9.814%   $260.2482   $260.25   $260.25   $260.20  
  Purchase #4 $166.58   6.619%   $177.6059   $177.61   $177.60   $177.60  
  Purchase #5 $45.37   8.225%   $49.1017   $49.10   $49.10   $49.10  
  Purchase #6 $121.75   10.771%   $134.8637   $134.86   $134.85   $134.90  
  Purchase #7 $134.36   12.611%   $151.3041   $151.30   $151.30   $151.30  
  7 purchase totals = $1,115.51       $1,226.0269   $1,226.02   $1,226.00   $1,226.00