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 $55.76   9.517%   $61.0667   $61.07   $61.05   $61.10  
  Purchase #2 $221.52   5.228%   $233.1011   $233.10   $233.10   $233.10  
  Purchase #3 $126.84   7.498%   $136.3505   $136.35   $136.35   $136.40  
  Purchase #4 $186.48   5.477%   $196.6935   $196.69   $196.70   $196.70  
  Purchase #5 $204.98   5.620%   $216.4999   $216.50   $216.50   $216.50  
  Purchase #6 $5.56   9.784%   $6.104   $6.10   $6.10   $6.10  
  Purchase #7 $48.26   12.311%   $54.2013   $54.20   $54.20   $54.20  
  7 purchase totals = $849.40       $904.0170   $904.01   $904.00   $904.10