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 $224.94   5.737%   $237.8448   $237.84   $237.85   $237.80  
  Purchase #2 $197.66   13.236%   $223.8223   $223.82   $223.80   $223.80  
  Purchase #3 $23.77   13.370%   $26.948   $26.95   $26.95   $26.90  
  Purchase #4 $55.69   5.659%   $58.8415   $58.84   $58.85   $58.80  
  Purchase #5 $208.71   6.151%   $221.5478   $221.55   $221.55   $221.50  
  Purchase #6 $224.49   7.651%   $241.6657   $241.67   $241.65   $241.70  
  Purchase #7 $57.86   11.714%   $64.6377   $64.64   $64.65   $64.60  
  7 purchase totals = $993.12       $1,075.3078   $1,075.31   $1,075.30   $1,075.10