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 $105.68   11.668%   $118.0107   $118.01   $118.00   $118.00  
  Purchase #2 $15.65   9.268%   $17.1004   $17.10   $17.10   $17.10  
  Purchase #3 $160.58   5.593%   $169.5612   $169.56   $169.55   $169.60  
  Purchase #4 $218.67   7.636%   $235.3676   $235.37   $235.35   $235.40  
  Purchase #5 $159.52   3.187%   $164.6039   $164.60   $164.60   $164.60  
  Purchase #6 $207.57   6.536%   $221.1368   $221.14   $221.15   $221.10  
  Purchase #7 $234.25   4.127%   $243.9175   $243.92   $243.90   $243.90  
  7 purchase totals = $1,101.92       $1,169.6981   $1,169.70   $1,169.65   $1,169.70