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 $160.89   8.681%   $174.8569   $174.86   $174.85   $174.90  
  Purchase #2 $90.76   4.730%   $95.0529   $95.05   $95.05   $95.10  
  Purchase #3 $157.83   9.682%   $173.1111   $173.11   $173.10   $173.10  
  Purchase #4 $133.48   12.110%   $149.6444   $149.64   $149.65   $149.60  
  Purchase #5 $195.71   9.334%   $213.9776   $213.98   $214.00   $214.00  
  Purchase #6 $32.28   4.601%   $33.7652   $33.77   $33.75   $33.80  
  Purchase #7 $178.33   3.220%   $184.0722   $184.07   $184.05   $184.10  
  7 purchase totals = $949.28       $1,024.4803   $1,024.48   $1,024.45   $1,024.60