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 $58.71   10.640%   $64.9567   $64.96   $64.95   $65.00  
  Purchase #2 $212.84   5.343%   $224.212   $224.21   $224.20   $224.20  
  Purchase #3 $144.42   4.657%   $151.1456   $151.15   $151.15   $151.10  
  Purchase #4 $71.83   11.654%   $80.2011   $80.20   $80.20   $80.20  
  Purchase #5 $195.74   8.411%   $212.2037   $212.20   $212.20   $212.20  
  Purchase #6 $249.82   12.872%   $281.9768   $281.98   $282.00   $282.00  
  Purchase #7 $196.41   8.771%   $213.6371   $213.64   $213.65   $213.60  
  7 purchase totals = $1,129.77       $1,228.3330   $1,228.34   $1,228.35   $1,228.30