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 $23.29   7.522%   $25.0419   $25.04   $25.05   $25.00  
  Purchase #2 $152.80   6.837%   $163.2469   $163.25   $163.25   $163.20  
  Purchase #3 $178.70   6.807%   $190.8641   $190.86   $190.85   $190.90  
  Purchase #4 $229.87   7.288%   $246.6229   $246.62   $246.60   $246.60  
  Purchase #5 $86.82   6.396%   $92.373   $92.37   $92.35   $92.40  
  Purchase #6 $215.52   8.221%   $233.2379   $233.24   $233.25   $233.20  
  Purchase #7 $5.64   7.290%   $6.0512   $6.05   $6.05   $6.10  
  7 purchase totals = $892.64       $957.4379   $957.43   $957.40   $957.40