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 $203.38   5.185%   $213.9253   $213.93   $213.95   $213.90  
  Purchase #2 $218.32   7.481%   $234.6525   $234.65   $234.65   $234.70  
  Purchase #3 $204.47   10.186%   $225.2973   $225.30   $225.30   $225.30  
  Purchase #4 $249.81   6.856%   $266.937   $266.94   $266.95   $266.90  
  Purchase #5 $103.42   3.246%   $106.777   $106.78   $106.80   $106.80  
  Purchase #6 $150.93   6.750%   $161.1178   $161.12   $161.10   $161.10  
  Purchase #7 $47.78   10.727%   $52.9054   $52.91   $52.90   $52.90  
  7 purchase totals = $1,178.11       $1,261.6123   $1,261.63   $1,261.65   $1,261.60