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 $147.50   6.428%   $156.9813   $156.98   $157.00   $157.00  
  Purchase #2 $197.46   4.258%   $205.8678   $205.87   $205.85   $205.90  
  Purchase #3 $224.81   5.586%   $237.3679   $237.37   $237.35   $237.40  
  Purchase #4 $230.80   5.837%   $244.2718   $244.27   $244.25   $244.30  
  Purchase #5 $245.84   6.272%   $261.2591   $261.26   $261.25   $261.30  
  Purchase #6 $31.56   6.819%   $33.7121   $33.71   $33.70   $33.70  
  Purchase #7 $115.77   6.138%   $122.876   $122.88   $122.90   $122.90  
  7 purchase totals = $1,193.74       $1,262.3360   $1,262.34   $1,262.30   $1,262.50