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 $70.46   5.238%   $74.1507   $74.15   $74.15   $74.20  
  Purchase #2 $160.76   4.255%   $167.6003   $167.60   $167.60   $167.60  
  Purchase #3 $157.38   3.147%   $162.3327   $162.33   $162.35   $162.30  
  Purchase #4 $59.44   4.386%   $62.047   $62.05   $62.05   $62.00  
  Purchase #5 $249.38   4.349%   $260.2255   $260.23   $260.25   $260.20  
  Purchase #6 $137.86   12.283%   $154.7933   $154.79   $154.80   $154.80  
  Purchase #7 $155.75   5.645%   $164.5421   $164.54   $164.55   $164.50  
  7 purchase totals = $991.03       $1,045.6916   $1,045.69   $1,045.75   $1,045.60