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 $53.67   10.803%   $59.468   $59.47   $59.45   $59.50  
  Purchase #2 $247.55   8.562%   $268.7452   $268.75   $268.75   $268.70  
  Purchase #3 $23.31   13.564%   $26.4718   $26.47   $26.45   $26.50  
  Purchase #4 $178.68   3.663%   $185.225   $185.23   $185.25   $185.20  
  Purchase #5 $216.30   8.624%   $234.9537   $234.95   $234.95   $235.00  
  Purchase #6 $205.36   6.158%   $218.0061   $218.01   $218.00   $218.00  
  Purchase #7 $174.79   3.687%   $181.2345   $181.23   $181.25   $181.20  
  7 purchase totals = $1,099.66       $1,174.1043   $1,174.11   $1,174.10   $1,174.10