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 $54.97   12.354%   $61.761   $61.76   $61.75   $61.80  
  Purchase #2 $95.32   8.507%   $103.4289   $103.43   $103.45   $103.40  
  Purchase #3 $239.60   5.297%   $252.2916   $252.29   $252.30   $252.30  
  Purchase #4 $220.77   6.110%   $234.259   $234.26   $234.25   $234.30  
  Purchase #5 $82.36   7.269%   $88.3467   $88.35   $88.35   $88.30  
  Purchase #6 $181.53   6.578%   $193.471   $193.47   $193.45   $193.50  
  Purchase #7 $193.54   3.666%   $200.6352   $200.64   $200.65   $200.60  
  7 purchase totals = $1,068.09       $1,134.1934   $1,134.20   $1,134.20   $1,134.20