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 $58.95   6.174%   $62.5896   $62.59   $62.60   $62.60  
  Purchase #2 $115.68   5.176%   $121.6676   $121.67   $121.65   $121.70  
  Purchase #3 $179.39   10.207%   $197.7003   $197.70   $197.70   $197.70  
  Purchase #4 $217.75   5.784%   $230.3447   $230.34   $230.35   $230.30  
  Purchase #5 $118.90   5.721%   $125.7023   $125.70   $125.70   $125.70  
  Purchase #6 $23.30   6.411%   $24.7938   $24.79   $24.80   $24.80  
  Purchase #7 $58.64   7.646%   $63.1236   $63.12   $63.10   $63.10  
  7 purchase totals = $772.61       $825.9219   $825.91   $825.90   $825.90