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 $182.56   9.289%   $199.518   $199.52   $199.50   $199.50  
  Purchase #2 $10.34   11.403%   $11.5191   $11.52   $11.50   $11.50  
  Purchase #3 $168.70   5.682%   $178.2855   $178.29   $178.30   $178.30  
  Purchase #4 $160.82   13.248%   $182.1254   $182.13   $182.15   $182.10  
  Purchase #5 $66.89   11.706%   $74.7201   $74.72   $74.70   $74.70  
  Purchase #6 $120.92   3.871%   $125.6008   $125.60   $125.60   $125.60  
  Purchase #7 $239.82   5.113%   $252.082   $252.08   $252.10   $252.10  
  7 purchase totals = $950.05       $1,023.8509   $1,023.86   $1,023.85   $1,023.80