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 $62.47   9.754%   $68.5633   $68.56   $68.55   $68.60  
  Purchase #2 $245.83   12.396%   $276.3031   $276.30   $276.30   $276.30  
  Purchase #3 $92.29   5.141%   $97.0346   $97.03   $97.05   $97.00  
  Purchase #4 $102.89   6.121%   $109.1879   $109.19   $109.20   $109.20  
  Purchase #5 $53.81   4.173%   $56.0555   $56.06   $56.05   $56.10  
  Purchase #6 $64.28   8.565%   $69.7856   $69.79   $69.80   $69.80  
  Purchase #7 $73.63   5.452%   $77.6443   $77.64   $77.65   $77.60  
  7 purchase totals = $695.20       $754.5743   $754.57   $754.60   $754.60