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 $88.51   7.851%   $95.4589   $95.46   $95.45   $95.50  
  Purchase #2 $164.96   4.781%   $172.8467   $172.85   $172.85   $172.80  
  Purchase #3 $81.29   4.776%   $85.1724   $85.17   $85.15   $85.20  
  Purchase #4 $106.68   13.851%   $121.4562   $121.46   $121.45   $121.50  
  Purchase #5 $14.57   10.493%   $16.0988   $16.10   $16.10   $16.10  
  Purchase #6 $104.54   3.485%   $108.1832   $108.18   $108.20   $108.20  
  Purchase #7 $236.81   12.455%   $266.3047   $266.30   $266.30   $266.30  
  7 purchase totals = $797.36       $865.5209   $865.52   $865.50   $865.60