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 $47.30   11.253%   $52.6227   $52.62   $52.60   $52.60  
  Purchase #2 $207.42   6.368%   $220.6285   $220.63   $220.65   $220.60  
  Purchase #3 $117.46   6.178%   $124.7167   $124.72   $124.70   $124.70  
  Purchase #4 $186.84   10.284%   $206.0546   $206.05   $206.05   $206.10  
  Purchase #5 $204.25   6.792%   $218.1227   $218.12   $218.10   $218.10  
  Purchase #6 $172.66   7.167%   $185.0345   $185.03   $185.05   $185.00  
  Purchase #7 $168.89   5.524%   $178.2195   $178.22   $178.20   $178.20  
  7 purchase totals = $1,104.82       $1,185.3992   $1,185.39   $1,185.35   $1,185.30