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 $67.72   8.264%   $73.3164   $73.32   $73.30   $73.30  
  Purchase #2 $220.47   10.524%   $243.6723   $243.67   $243.65   $243.70  
  Purchase #3 $130.99   9.339%   $143.2232   $143.22   $143.20   $143.20  
  Purchase #4 $215.89   12.527%   $242.9345   $242.93   $242.95   $242.90  
  Purchase #5 $158.94   11.593%   $177.3659   $177.37   $177.35   $177.40  
  Purchase #6 $155.38   4.379%   $162.1841   $162.18   $162.20   $162.20  
  Purchase #7 $106.61   8.137%   $115.2849   $115.28   $115.30   $115.30  
  7 purchase totals = $1,056.00       $1,157.9813   $1,157.97   $1,157.95   $1,158.00