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 $196.71   11.661%   $219.6484   $219.65   $219.65   $219.60  
  Purchase #2 $58.90   12.351%   $66.1747   $66.17   $66.15   $66.20  
  Purchase #3 $93.59   4.618%   $97.912   $97.91   $97.90   $97.90  
  Purchase #4 $108.51   3.795%   $112.628   $112.63   $112.65   $112.60  
  Purchase #5 $213.87   7.580%   $230.0813   $230.08   $230.10   $230.10  
  Purchase #6 $215.45   6.823%   $230.1502   $230.15   $230.15   $230.20  
  Purchase #7 $228.93   7.573%   $246.2669   $246.27   $246.25   $246.30  
  7 purchase totals = $1,115.96       $1,202.8615   $1,202.86   $1,202.85   $1,202.90