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 $103.85   9.237%   $113.4426   $113.44   $113.45   $113.40  
  Purchase #2 $232.31   3.859%   $241.2748   $241.27   $241.25   $241.30  
  Purchase #3 $188.37   6.820%   $201.2168   $201.22   $201.20   $201.20  
  Purchase #4 $57.75   6.381%   $61.435   $61.44   $61.45   $61.40  
  Purchase #5 $94.37   4.221%   $98.3534   $98.35   $98.35   $98.40  
  Purchase #6 $17.53   9.652%   $19.222   $19.22   $19.20   $19.20  
  Purchase #7 $243.40   13.378%   $275.9621   $275.96   $275.95   $276.00  
  7 purchase totals = $937.58       $1,010.9067   $1,010.90   $1,010.85   $1,010.90