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 $56.31   10.364%   $62.146   $62.15   $62.15   $62.10  
  Purchase #2 $88.66   10.491%   $97.9613   $97.96   $97.95   $98.00  
  Purchase #3 $97.96   7.149%   $104.9632   $104.96   $104.95   $105.00  
  Purchase #4 $76.77   13.399%   $87.0564   $87.06   $87.05   $87.10  
  Purchase #5 $36.74   12.610%   $41.3729   $41.37   $41.35   $41.40  
  Purchase #6 $210.31   5.488%   $221.8518   $221.85   $221.85   $221.90  
  Purchase #7 $218.79   6.284%   $232.5388   $232.54   $232.55   $232.50  
  7 purchase totals = $785.54       $847.8904   $847.89   $847.85   $848.00