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 $81.58   13.544%   $92.6292   $92.63   $92.65   $92.60  
  Purchase #2 $186.67   12.151%   $209.3523   $209.35   $209.35   $209.40  
  Purchase #3 $89.63   5.459%   $94.5229   $94.52   $94.50   $94.50  
  Purchase #4 $87.90   6.311%   $93.4474   $93.45   $93.45   $93.40  
  Purchase #5 $59.30   3.372%   $61.2996   $61.30   $61.30   $61.30  
  Purchase #6 $215.30   4.707%   $225.4342   $225.43   $225.45   $225.40  
  Purchase #7 $187.76   11.734%   $209.7918   $209.79   $209.80   $209.80  
  7 purchase totals = $908.14       $986.4774   $986.47   $986.50   $986.40