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 $108.37   7.735%   $116.7524   $116.75   $116.75   $116.80  
  Purchase #2 $236.76   6.107%   $251.2189   $251.22   $251.20   $251.20  
  Purchase #3 $59.82   3.798%   $62.092   $62.09   $62.10   $62.10  
  Purchase #4 $250.81   8.394%   $271.863   $271.86   $271.85   $271.90  
  Purchase #5 $197.48   10.684%   $218.5788   $218.58   $218.60   $218.60  
  Purchase #6 $237.96   7.874%   $256.697   $256.70   $256.70   $256.70  
  Purchase #7 $211.48   6.121%   $224.4247   $224.42   $224.40   $224.40  
  7 purchase totals = $1,302.68       $1,401.6268   $1,401.62   $1,401.60   $1,401.70