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 $94.38   3.483%   $97.6673   $97.67   $97.65   $97.70  
  Purchase #2 $101.80   11.398%   $113.4032   $113.40   $113.40   $113.40  
  Purchase #3 $146.87   7.703%   $158.1834   $158.18   $158.20   $158.20  
  Purchase #4 $189.87   3.381%   $196.2895   $196.29   $196.30   $196.30  
  Purchase #5 $186.63   4.110%   $194.3005   $194.30   $194.30   $194.30  
  Purchase #6 $220.51   12.643%   $248.3891   $248.39   $248.40   $248.40  
  Purchase #7 $25.59   8.122%   $27.6684   $27.67   $27.65   $27.70  
  7 purchase totals = $965.65       $1,035.9014   $1,035.90   $1,035.90   $1,036.00