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 $69.61   7.568%   $74.8781   $74.88   $74.90   $74.90  
  Purchase #2 $214.27   10.759%   $237.3233   $237.32   $237.30   $237.30  
  Purchase #3 $160.86   12.301%   $180.6474   $180.65   $180.65   $180.60  
  Purchase #4 $195.60   7.476%   $210.2231   $210.22   $210.20   $210.20  
  Purchase #5 $144.41   7.611%   $155.401   $155.40   $155.40   $155.40  
  Purchase #6 $84.77   4.234%   $88.3592   $88.36   $88.35   $88.40  
  Purchase #7 $61.38   5.765%   $64.9186   $64.92   $64.90   $64.90  
  7 purchase totals = $930.90       $1,011.7507   $1,011.75   $1,011.70   $1,011.70