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 $86.61   7.329%   $92.9576   $92.96   $92.95   $93.00  
  Purchase #2 $169.26   7.705%   $182.3015   $182.30   $182.30   $182.30  
  Purchase #3 $19.25   7.724%   $20.7369   $20.74   $20.75   $20.70  
  Purchase #4 $180.66   7.144%   $193.5664   $193.57   $193.55   $193.60  
  Purchase #5 $215.61   12.806%   $243.221   $243.22   $243.20   $243.20  
  Purchase #6 $187.44   13.717%   $213.1511   $213.15   $213.15   $213.20  
  Purchase #7 $194.43   4.567%   $203.3096   $203.31   $203.30   $203.30  
  7 purchase totals = $1,053.26       $1,149.2441   $1,149.25   $1,149.20   $1,149.30