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 $55.51   7.272%   $59.5467   $59.55   $59.55   $59.50  
  Purchase #2 $243.62   3.182%   $251.372   $251.37   $251.35   $251.40  
  Purchase #3 $100.65   5.429%   $106.1143   $106.11   $106.10   $106.10  
  Purchase #4 $188.49   5.256%   $198.397   $198.40   $198.40   $198.40  
  Purchase #5 $237.73   3.585%   $246.2526   $246.25   $246.25   $246.30  
  Purchase #6 $173.28   10.157%   $190.88   $190.88   $190.90   $190.90  
  Purchase #7 $91.70   10.786%   $101.5908   $101.59   $101.60   $101.60  
  7 purchase totals = $1,090.98       $1,154.1534   $1,154.15   $1,154.15   $1,154.20