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 $97.39   9.619%   $106.7579   $106.76   $106.75   $106.80  
  Purchase #2 $214.93   7.817%   $231.7311   $231.73   $231.75   $231.70  
  Purchase #3 $15.47   12.697%   $17.4342   $17.43   $17.45   $17.40  
  Purchase #4 $182.93   9.694%   $200.6632   $200.66   $200.65   $200.70  
  Purchase #5 $162.85   5.345%   $171.5543   $171.55   $171.55   $171.60  
  Purchase #6 $239.36   13.410%   $271.4582   $271.46   $271.45   $271.50  
  Purchase #7 $121.35   4.316%   $126.5875   $126.59   $126.60   $126.60  
  7 purchase totals = $1,034.28       $1,126.1864   $1,126.18   $1,126.20   $1,126.30