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 $84.40   11.780%   $94.3423   $94.34   $94.35   $94.30  
  Purchase #2 $152.42   12.147%   $170.9345   $170.93   $170.95   $170.90  
  Purchase #3 $19.75   8.604%   $21.4493   $21.45   $21.45   $21.40  
  Purchase #4 $112.38   5.776%   $118.8711   $118.87   $118.85   $118.90  
  Purchase #5 $200.33   6.702%   $213.7561   $213.76   $213.75   $213.80  
  Purchase #6 $225.51   10.280%   $248.6924   $248.69   $248.70   $248.70  
  Purchase #7 $246.50   4.444%   $257.4545   $257.45   $257.45   $257.50  
  7 purchase totals = $1,041.29       $1,125.5002   $1,125.49   $1,125.50   $1,125.50