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 $62.51   11.146%   $69.4774   $69.48   $69.50   $69.50  
  Purchase #2 $139.60   9.711%   $153.1566   $153.16   $153.15   $153.20  
  Purchase #3 $250.37   4.714%   $262.1724   $262.17   $262.15   $262.20  
  Purchase #4 $123.44   11.539%   $137.6837   $137.68   $137.70   $137.70  
  Purchase #5 $202.62   8.426%   $219.6928   $219.69   $219.70   $219.70  
  Purchase #6 $227.97   5.341%   $240.1459   $240.15   $240.15   $240.10  
  Purchase #7 $37.56   11.168%   $41.7547   $41.75   $41.75   $41.80  
  7 purchase totals = $1,044.07       $1,124.0835   $1,124.08   $1,124.10   $1,124.20