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 $63.25   13.762%   $71.9545   $71.95   $71.95   $72.00  
  Purchase #2 $195.88   4.202%   $204.1109   $204.11   $204.10   $204.10  
  Purchase #3 $227.51   10.401%   $251.1733   $251.17   $251.15   $251.20  
  Purchase #4 $147.55   9.816%   $162.0335   $162.03   $162.05   $162.00  
  Purchase #5 $96.76   8.430%   $104.9169   $104.92   $104.90   $104.90  
  Purchase #6 $147.27   6.870%   $157.3874   $157.39   $157.40   $157.40  
  Purchase #7 $245.35   10.197%   $270.3683   $270.37   $270.35   $270.40  
  7 purchase totals = $1,123.57       $1,221.9448   $1,221.94   $1,221.90   $1,222.00