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 $196.50   5.838%   $207.9717   $207.97   $207.95   $208.00  
  Purchase #2 $228.78   10.421%   $252.6212   $252.62   $252.60   $252.60  
  Purchase #3 $47.42   7.276%   $50.8703   $50.87   $50.85   $50.90  
  Purchase #4 $158.70   7.410%   $170.4597   $170.46   $170.45   $170.50  
  Purchase #5 $233.51   3.251%   $241.1014   $241.10   $241.10   $241.10  
  Purchase #6 $34.31   7.503%   $36.8843   $36.88   $36.90   $36.90  
  Purchase #7 $44.39   9.408%   $48.5662   $48.57   $48.55   $48.60  
  7 purchase totals = $943.61       $1,008.4748   $1,008.47   $1,008.40   $1,008.60