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 $119.36   5.259%   $125.6371   $125.64   $125.65   $125.60  
  Purchase #2 $217.31   3.677%   $225.3005   $225.30   $225.30   $225.30  
  Purchase #3 $30.85   9.397%   $33.749   $33.75   $33.75   $33.70  
  Purchase #4 $245.55   8.362%   $266.0829   $266.08   $266.10   $266.10  
  Purchase #5 $240.81   11.295%   $268.0095   $268.01   $268.00   $268.00  
  Purchase #6 $220.36   10.577%   $243.6675   $243.67   $243.65   $243.70  
  Purchase #7 $128.91   11.220%   $143.3737   $143.37   $143.35   $143.40  
  7 purchase totals = $1,203.15       $1,305.8202   $1,305.82   $1,305.80   $1,305.80