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 $179.86   13.514%   $204.1663   $204.17   $204.15   $204.20  
  Purchase #2 $213.53   9.119%   $233.0018   $233.00   $233.00   $233.00  
  Purchase #3 $192.52   9.549%   $210.9037   $210.90   $210.90   $210.90  
  Purchase #4 $47.40   7.331%   $50.8749   $50.87   $50.85   $50.90  
  Purchase #5 $106.25   10.800%   $117.725   $117.73   $117.75   $117.70  
  Purchase #6 $210.43   12.290%   $236.2918   $236.29   $236.30   $236.30  
  Purchase #7 $64.71   12.210%   $72.6111   $72.61   $72.60   $72.60  
  7 purchase totals = $1,014.70       $1,125.5746   $1,125.57   $1,125.55   $1,125.60