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 $125.95   6.255%   $133.8282   $133.83   $133.85   $133.80  
  Purchase #2 $203.94   3.760%   $211.6081   $211.61   $211.60   $211.60  
  Purchase #3 $205.82   7.696%   $221.6599   $221.66   $221.65   $221.70  
  Purchase #4 $95.83   6.574%   $102.1299   $102.13   $102.15   $102.10  
  Purchase #5 $212.78   13.562%   $241.6372   $241.64   $241.65   $241.60  
  Purchase #6 $24.80   6.525%   $26.4182   $26.42   $26.40   $26.40  
  Purchase #7 $127.77   3.692%   $132.4873   $132.49   $132.50   $132.50  
  7 purchase totals = $996.89       $1,069.7688   $1,069.78   $1,069.80   $1,069.70