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 $59.76   12.689%   $67.3429   $67.34   $67.35   $67.30  
  Purchase #2 $200.68   5.871%   $212.4619   $212.46   $212.45   $212.50  
  Purchase #3 $212.46   13.748%   $241.669   $241.67   $241.65   $241.70  
  Purchase #4 $206.44   3.422%   $213.5044   $213.50   $213.50   $213.50  
  Purchase #5 $188.48   9.190%   $205.8013   $205.80   $205.80   $205.80  
  Purchase #6 $187.92   6.314%   $199.7853   $199.79   $199.80   $199.80  
  Purchase #7 $146.71   9.442%   $160.5624   $160.56   $160.55   $160.60  
  7 purchase totals = $1,202.45       $1,301.1272   $1,301.12   $1,301.10   $1,301.20