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 $210.84   3.312%   $217.823   $217.82   $217.80   $217.80  
  Purchase #2 $205.38   12.391%   $230.8286   $230.83   $230.85   $230.80  
  Purchase #3 $205.53   7.131%   $220.1863   $220.19   $220.20   $220.20  
  Purchase #4 $125.59   6.450%   $133.6906   $133.69   $133.70   $133.70  
  Purchase #5 $180.91   12.377%   $203.3012   $203.30   $203.30   $203.30  
  Purchase #6 $246.76   5.179%   $259.5397   $259.54   $259.55   $259.50  
  Purchase #7 $157.85   13.201%   $178.6878   $178.69   $178.70   $178.70  
  7 purchase totals = $1,332.86       $1,444.0572   $1,444.06   $1,444.10   $1,444.00