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 $65.34   13.691%   $74.2857   $74.29   $74.30   $74.30  
  Purchase #2 $48.55   9.575%   $53.1987   $53.20   $53.20   $53.20  
  Purchase #3 $100.70   7.419%   $108.1709   $108.17   $108.15   $108.20  
  Purchase #4 $185.57   6.334%   $197.324   $197.32   $197.30   $197.30  
  Purchase #5 $236.44   6.454%   $251.6998   $251.70   $251.70   $251.70  
  Purchase #6 $138.52   3.354%   $143.166   $143.17   $143.15   $143.20  
  Purchase #7 $172.28   8.797%   $187.4355   $187.44   $187.45   $187.40  
  7 purchase totals = $947.40       $1,015.2806   $1,015.29   $1,015.25   $1,015.30