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 $46.82   3.274%   $48.3529   $48.35   $48.35   $48.40  
  Purchase #2 $9.83   8.766%   $10.6917   $10.69   $10.70   $10.70  
  Purchase #3 $241.45   4.173%   $251.5257   $251.53   $251.55   $251.50  
  Purchase #4 $110.98   13.324%   $125.767   $125.77   $125.75   $125.80  
  Purchase #5 $228.80   3.701%   $237.2679   $237.27   $237.25   $237.30  
  Purchase #6 $200.80   9.824%   $220.5266   $220.53   $220.55   $220.50  
  Purchase #7 $192.48   10.771%   $213.212   $213.21   $213.20   $213.20  
  7 purchase totals = $1,031.16       $1,107.3438   $1,107.35   $1,107.35   $1,107.40