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 $8.86   9.154%   $9.671   $9.67   $9.65   $9.70  
  Purchase #2 $174.49   3.762%   $181.0543   $181.05   $181.05   $181.10  
  Purchase #3 $61.69   13.487%   $70.0101   $70.01   $70.00   $70.00  
  Purchase #4 $216.39   4.401%   $225.9133   $225.91   $225.90   $225.90  
  Purchase #5 $245.44   7.478%   $263.794   $263.79   $263.80   $263.80  
  Purchase #6 $187.41   5.481%   $197.6819   $197.68   $197.70   $197.70  
  Purchase #7 $144.63   12.581%   $162.8259   $162.83   $162.85   $162.80  
  7 purchase totals = $1,038.91       $1,110.9505   $1,110.94   $1,110.95   $1,111.00