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 $214.39   6.184%   $227.6479   $227.65   $227.65   $227.60  
  Purchase #2 $119.56   10.840%   $132.5203   $132.52   $132.50   $132.50  
  Purchase #3 $157.55   13.438%   $178.7216   $178.72   $178.70   $178.70  
  Purchase #4 $131.29   8.460%   $142.3971   $142.40   $142.40   $142.40  
  Purchase #5 $62.83   8.592%   $68.2284   $68.23   $68.25   $68.20  
  Purchase #6 $235.55   6.309%   $250.4108   $250.41   $250.40   $250.40  
  Purchase #7 $46.56   6.690%   $49.6749   $49.67   $49.65   $49.70  
  7 purchase totals = $967.73       $1,049.6010   $1,049.60   $1,049.55   $1,049.50