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 $114.88   6.250%   $122.06   $122.06   $122.05   $122.10  
  Purchase #2 $95.80   10.490%   $105.8494   $105.85   $105.85   $105.80  
  Purchase #3 $188.66   12.345%   $211.9501   $211.95   $211.95   $212.00  
  Purchase #4 $200.37   7.281%   $214.9589   $214.96   $214.95   $215.00  
  Purchase #5 $181.31   6.576%   $193.2329   $193.23   $193.25   $193.20  
  Purchase #6 $176.50   11.184%   $196.2398   $196.24   $196.25   $196.20  
  Purchase #7 $65.95   12.717%   $74.3369   $74.34   $74.35   $74.30  
  7 purchase totals = $1,023.47       $1,118.6280   $1,118.63   $1,118.65   $1,118.60