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 $84.33   13.750%   $95.9254   $95.93   $95.95   $95.90  
  Purchase #2 $120.54   9.574%   $132.0805   $132.08   $132.10   $132.10  
  Purchase #3 $144.39   13.176%   $163.4148   $163.41   $163.40   $163.40  
  Purchase #4 $167.42   3.518%   $173.3098   $173.31   $173.30   $173.30  
  Purchase #5 $222.72   4.731%   $233.2569   $233.26   $233.25   $233.30  
  Purchase #6 $11.45   9.874%   $12.5806   $12.58   $12.60   $12.60  
  Purchase #7 $145.80   3.146%   $150.3869   $150.39   $150.40   $150.40  
  7 purchase totals = $896.65       $960.9549   $960.96   $961.00   $961.00