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 $211.81   10.167%   $233.3447   $233.34   $233.35   $233.30  
  Purchase #2 $247.56   11.272%   $275.465   $275.47   $275.45   $275.50  
  Purchase #3 $10.84   8.488%   $11.7601   $11.76   $11.75   $11.80  
  Purchase #4 $244.73   6.224%   $259.962   $259.96   $259.95   $260.00  
  Purchase #5 $240.80   11.531%   $268.5666   $268.57   $268.55   $268.60  
  Purchase #6 $71.40   4.455%   $74.5809   $74.58   $74.60   $74.60  
  Purchase #7 $163.84   4.544%   $171.2849   $171.28   $171.30   $171.30  
  7 purchase totals = $1,190.98       $1,294.9642   $1,294.96   $1,294.95   $1,295.10