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 $182.51   13.268%   $206.7254   $206.73   $206.75   $206.70  
  Purchase #2 $248.30   4.740%   $260.0694   $260.07   $260.05   $260.10  
  Purchase #3 $228.58   11.138%   $254.0392   $254.04   $254.05   $254.00  
  Purchase #4 $231.60   10.573%   $256.0871   $256.09   $256.10   $256.10  
  Purchase #5 $215.62   6.833%   $230.3533   $230.35   $230.35   $230.40  
  Purchase #6 $36.64   4.143%   $38.158   $38.16   $38.15   $38.20  
  Purchase #7 $44.57   11.842%   $49.848   $49.85   $49.85   $49.80  
  7 purchase totals = $1,187.82       $1,295.2804   $1,295.29   $1,295.30   $1,295.30