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 $106.48   7.637%   $114.6119   $114.61   $114.60   $114.60  
  Purchase #2 $24.79   4.252%   $25.8441   $25.84   $25.85   $25.80  
  Purchase #3 $159.35   9.218%   $174.0389   $174.04   $174.05   $174.00  
  Purchase #4 $208.43   4.688%   $218.2012   $218.20   $218.20   $218.20  
  Purchase #5 $80.96   7.788%   $87.2652   $87.27   $87.25   $87.30  
  Purchase #6 $106.73   3.849%   $110.838   $110.84   $110.85   $110.80  
  Purchase #7 $14.30   3.299%   $14.7718   $14.77   $14.75   $14.80  
  7 purchase totals = $701.04       $745.5711   $745.57   $745.55   $745.50