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 $182.97   7.371%   $196.4567   $196.46   $196.45   $196.50  
  Purchase #2 $63.76   4.386%   $66.5565   $66.56   $66.55   $66.60  
  Purchase #3 $102.90   4.364%   $107.3906   $107.39   $107.40   $107.40  
  Purchase #4 $93.49   13.352%   $105.9728   $105.97   $105.95   $106.00  
  Purchase #5 $153.56   6.617%   $163.7211   $163.72   $163.70   $163.70  
  Purchase #6 $153.77   8.230%   $166.4253   $166.43   $166.45   $166.40  
  Purchase #7 $127.83   5.601%   $134.9898   $134.99   $135.00   $135.00  
  7 purchase totals = $878.28       $941.5128   $941.52   $941.50   $941.60