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 $91.37   3.677%   $94.7297   $94.73   $94.75   $94.70  
  Purchase #2 $192.76   7.629%   $207.4657   $207.47   $207.45   $207.50  
  Purchase #3 $241.87   13.636%   $274.8514   $274.85   $274.85   $274.90  
  Purchase #4 $106.62   9.531%   $116.782   $116.78   $116.80   $116.80  
  Purchase #5 $198.33   9.660%   $217.4887   $217.49   $217.50   $217.50  
  Purchase #6 $41.49   4.366%   $43.3015   $43.30   $43.30   $43.30  
  Purchase #7 $228.58   8.797%   $248.6882   $248.69   $248.70   $248.70  
  7 purchase totals = $1,101.02       $1,203.3072   $1,203.31   $1,203.35   $1,203.40