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 $182.75   8.123%   $197.5948   $197.59   $197.60   $197.60  
  Purchase #2 $217.46   12.752%   $245.1905   $245.19   $245.20   $245.20  
  Purchase #3 $241.37   5.302%   $254.1674   $254.17   $254.15   $254.20  
  Purchase #4 $164.64   9.471%   $180.2331   $180.23   $180.25   $180.20  
  Purchase #5 $212.99   8.350%   $230.7747   $230.77   $230.75   $230.80  
  Purchase #6 $52.48   3.428%   $54.279   $54.28   $54.30   $54.30  
  Purchase #7 $214.76   3.630%   $222.5558   $222.56   $222.55   $222.60  
  7 purchase totals = $1,286.45       $1,384.7953   $1,384.79   $1,384.80   $1,384.90