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 $174.41   13.351%   $197.6955   $197.70   $197.70   $197.70  
  Purchase #2 $230.48   6.333%   $245.0763   $245.08   $245.10   $245.10  
  Purchase #3 $35.61   8.455%   $38.6208   $38.62   $38.60   $38.60  
  Purchase #4 $198.61   11.442%   $221.335   $221.34   $221.35   $221.30  
  Purchase #5 $111.86   12.184%   $125.489   $125.49   $125.50   $125.50  
  Purchase #6 $119.90   8.205%   $129.7378   $129.74   $129.75   $129.70  
  Purchase #7 $53.72   4.775%   $56.2851   $56.29   $56.30   $56.30  
  7 purchase totals = $924.59       $1,014.2395   $1,014.26   $1,014.30   $1,014.20