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 $62.53   4.497%   $65.342   $65.34   $65.35   $65.30  
  Purchase #2 $187.58   10.850%   $207.9324   $207.93   $207.95   $207.90  
  Purchase #3 $71.28   3.548%   $73.809   $73.81   $73.80   $73.80  
  Purchase #4 $195.91   11.822%   $219.0705   $219.07   $219.05   $219.10  
  Purchase #5 $188.37   8.403%   $204.1987   $204.20   $204.20   $204.20  
  Purchase #6 $27.93   7.343%   $29.9809   $29.98   $30.00   $30.00  
  Purchase #7 $193.27   10.552%   $213.6639   $213.66   $213.65   $213.70  
  7 purchase totals = $926.87       $1,013.9974   $1,013.99   $1,014.00   $1,014.00