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 $114.70   3.427%   $118.6308   $118.63   $118.65   $118.60  
  Purchase #2 $143.57   8.332%   $155.5323   $155.53   $155.55   $155.50  
  Purchase #3 $151.83   8.561%   $164.8282   $164.83   $164.85   $164.80  
  Purchase #4 $210.45   4.480%   $219.8782   $219.88   $219.90   $219.90  
  Purchase #5 $13.66   6.120%   $14.496   $14.50   $14.50   $14.50  
  Purchase #6 $155.34   13.306%   $176.0095   $176.01   $176.00   $176.00  
  Purchase #7 $218.32   4.334%   $227.782   $227.78   $227.80   $227.80  
  7 purchase totals = $1,007.87       $1,077.1570   $1,077.16   $1,077.25   $1,077.10