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 $87.86   9.547%   $96.248   $96.25   $96.25   $96.20  
  Purchase #2 $57.40   10.766%   $63.5797   $63.58   $63.60   $63.60  
  Purchase #3 $83.85   4.309%   $87.4631   $87.46   $87.45   $87.50  
  Purchase #4 $228.44   10.264%   $251.8871   $251.89   $251.90   $251.90  
  Purchase #5 $122.61   8.560%   $133.1054   $133.11   $133.10   $133.10  
  Purchase #6 $199.26   5.647%   $210.5122   $210.51   $210.50   $210.50  
  Purchase #7 $216.86   4.180%   $225.9247   $225.92   $225.90   $225.90  
  7 purchase totals = $996.28       $1,068.7202   $1,068.72   $1,068.70   $1,068.70