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 $143.28   7.479%   $153.9959   $154.00   $154.00   $154.00  
  Purchase #2 $172.30   6.565%   $183.6115   $183.61   $183.60   $183.60  
  Purchase #3 $160.34   8.180%   $173.4558   $173.46   $173.45   $173.50  
  Purchase #4 $244.83   6.704%   $261.2434   $261.24   $261.25   $261.20  
  Purchase #5 $104.99   6.223%   $111.5235   $111.52   $111.50   $111.50  
  Purchase #6 $245.61   4.544%   $256.7705   $256.77   $256.75   $256.80  
  Purchase #7 $119.48   5.759%   $126.3609   $126.36   $126.35   $126.40  
  7 purchase totals = $1,190.83       $1,266.9615   $1,266.96   $1,266.90   $1,267.00