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 $228.53   6.816%   $244.1066   $244.11   $244.10   $244.10  
  Purchase #2 $193.34   6.221%   $205.3677   $205.37   $205.35   $205.40  
  Purchase #3 $43.82   13.432%   $49.7059   $49.71   $49.70   $49.70  
  Purchase #4 $189.65   5.605%   $200.2799   $200.28   $200.30   $200.30  
  Purchase #5 $44.45   8.480%   $48.2194   $48.22   $48.20   $48.20  
  Purchase #6 $230.38   5.287%   $242.5602   $242.56   $242.55   $242.60  
  Purchase #7 $219.42   7.862%   $236.6708   $236.67   $236.65   $236.70  
  7 purchase totals = $1,149.59       $1,226.9105   $1,226.92   $1,226.85   $1,227.00