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 $60.95   6.532%   $64.9313   $64.93   $64.95   $64.90  
  Purchase #2 $169.60   7.648%   $182.571   $182.57   $182.55   $182.60  
  Purchase #3 $219.32   8.493%   $237.9468   $237.95   $237.95   $237.90  
  Purchase #4 $27.66   13.749%   $31.463   $31.46   $31.45   $31.50  
  Purchase #5 $114.86   7.531%   $123.5101   $123.51   $123.50   $123.50  
  Purchase #6 $170.79   12.525%   $192.1814   $192.18   $192.20   $192.20  
  Purchase #7 $231.78   10.603%   $256.3556   $256.36   $256.35   $256.40  
  7 purchase totals = $994.96       $1,088.9592   $1,088.96   $1,088.95   $1,089.00