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 $163.39   11.797%   $182.6651   $182.67   $182.65   $182.70  
  Purchase #2 $170.64   11.119%   $189.6135   $189.61   $189.60   $189.60  
  Purchase #3 $84.29   12.472%   $94.8026   $94.80   $94.80   $94.80  
  Purchase #4 $86.38   8.502%   $93.724   $93.72   $93.70   $93.70  
  Purchase #5 $145.82   11.310%   $162.3122   $162.31   $162.30   $162.30  
  Purchase #6 $184.56   9.173%   $201.4897   $201.49   $201.50   $201.50  
  Purchase #7 $98.53   3.724%   $102.1993   $102.20   $102.20   $102.20  
  7 purchase totals = $933.61       $1,026.8064   $1,026.80   $1,026.75   $1,026.80