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 $62.25   11.318%   $69.2955   $69.30   $69.30   $69.30  
  Purchase #2 $144.44   6.582%   $153.947   $153.95   $153.95   $153.90  
  Purchase #3 $197.73   11.731%   $220.9257   $220.93   $220.95   $220.90  
  Purchase #4 $56.30   9.381%   $61.5815   $61.58   $61.60   $61.60  
  Purchase #5 $149.69   10.356%   $165.1919   $165.19   $165.20   $165.20  
  Purchase #6 $214.41   3.779%   $222.5126   $222.51   $222.50   $222.50  
  Purchase #7 $111.49   3.409%   $115.2907   $115.29   $115.30   $115.30  
  7 purchase totals = $936.31       $1,008.7449   $1,008.75   $1,008.80   $1,008.70