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 $191.86   4.120%   $199.7646   $199.76   $199.75   $199.80  
  Purchase #2 $97.97   3.571%   $101.4685   $101.47   $101.45   $101.50  
  Purchase #3 $115.37   3.396%   $119.288   $119.29   $119.30   $119.30  
  Purchase #4 $68.95   7.414%   $74.062   $74.06   $74.05   $74.10  
  Purchase #5 $85.60   4.443%   $89.4032   $89.40   $89.40   $89.40  
  Purchase #6 $235.45   12.278%   $264.3586   $264.36   $264.35   $264.40  
  Purchase #7 $24.47   8.530%   $26.5573   $26.56   $26.55   $26.60  
  7 purchase totals = $819.67       $874.9022   $874.90   $874.85   $875.10