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 $196.57   4.202%   $204.8299   $204.83   $204.85   $204.80  
  Purchase #2 $73.47   5.290%   $77.3566   $77.36   $77.35   $77.40  
  Purchase #3 $64.79   4.726%   $67.852   $67.85   $67.85   $67.90  
  Purchase #4 $40.45   7.332%   $43.4158   $43.42   $43.40   $43.40  
  Purchase #5 $194.90   4.691%   $204.0428   $204.04   $204.05   $204.00  
  Purchase #6 $196.81   5.521%   $207.6759   $207.68   $207.70   $207.70  
  Purchase #7 $182.29   13.323%   $206.5765   $206.58   $206.60   $206.60  
  7 purchase totals = $949.28       $1,011.7495   $1,011.76   $1,011.80   $1,011.80