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 $241.26   9.146%   $263.3256   $263.33   $263.35   $263.30  
  Purchase #2 $246.71   9.372%   $269.8317   $269.83   $269.85   $269.80  
  Purchase #3 $173.81   8.213%   $188.085   $188.09   $188.10   $188.10  
  Purchase #4 $90.71   4.677%   $94.9525   $94.95   $94.95   $95.00  
  Purchase #5 $204.36   13.464%   $231.875   $231.88   $231.90   $231.90  
  Purchase #6 $213.45   5.111%   $224.3594   $224.36   $224.35   $224.40  
  Purchase #7 $180.54   7.191%   $193.5226   $193.52   $193.50   $193.50  
  7 purchase totals = $1,350.84       $1,465.9518   $1,465.96   $1,466.00   $1,466.00