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 $88.83   7.378%   $95.3839   $95.38   $95.40   $95.40  
  Purchase #2 $173.82   3.187%   $179.3596   $179.36   $179.35   $179.40  
  Purchase #3 $229.64   12.837%   $259.1189   $259.12   $259.10   $259.10  
  Purchase #4 $138.37   13.825%   $157.4997   $157.50   $157.50   $157.50  
  Purchase #5 $34.42   4.868%   $36.0956   $36.10   $36.10   $36.10  
  Purchase #6 $207.84   13.233%   $235.3435   $235.34   $235.35   $235.30  
  Purchase #7 $229.58   5.243%   $241.6169   $241.62   $241.60   $241.60  
  7 purchase totals = $1,102.50       $1,204.4181   $1,204.42   $1,204.40   $1,204.40