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 $22.39   5.399%   $23.5988   $23.60   $23.60   $23.60  
  Purchase #2 $241.50   13.661%   $274.4913   $274.49   $274.50   $274.50  
  Purchase #3 $174.42   8.868%   $189.8876   $189.89   $189.90   $189.90  
  Purchase #4 $90.53   5.586%   $95.587   $95.59   $95.60   $95.60  
  Purchase #5 $23.93   13.464%   $27.1519   $27.15   $27.15   $27.20  
  Purchase #6 $219.30   4.572%   $229.3264   $229.33   $229.35   $229.30  
  Purchase #7 $192.90   6.209%   $204.8772   $204.88   $204.90   $204.90  
  7 purchase totals = $964.97       $1,044.9202   $1,044.93   $1,045.00   $1,045.00