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 $183.57   9.627%   $201.2423   $201.24   $201.25   $201.20  
  Purchase #2 $126.49   11.840%   $141.4664   $141.47   $141.45   $141.50  
  Purchase #3 $65.61   12.695%   $73.9392   $73.94   $73.95   $73.90  
  Purchase #4 $155.29   4.272%   $161.924   $161.92   $161.90   $161.90  
  Purchase #5 $212.89   12.159%   $238.7753   $238.78   $238.80   $238.80  
  Purchase #6 $170.78   4.582%   $178.6051   $178.61   $178.60   $178.60  
  Purchase #7 $107.71   7.430%   $115.7129   $115.71   $115.70   $115.70  
  7 purchase totals = $1,022.34       $1,111.6652   $1,111.67   $1,111.65   $1,111.60