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 $89.71   5.820%   $94.9311   $94.93   $94.95   $94.90  
  Purchase #2 $157.53   11.540%   $175.709   $175.71   $175.70   $175.70  
  Purchase #3 $156.57   12.409%   $175.9988   $176.00   $176.00   $176.00  
  Purchase #4 $139.46   11.784%   $155.894   $155.89   $155.90   $155.90  
  Purchase #5 $111.34   4.718%   $116.593   $116.59   $116.60   $116.60  
  Purchase #6 $36.58   8.459%   $39.6743   $39.67   $39.65   $39.70  
  Purchase #7 $5.58   7.602%   $6.0042   $6.00   $6.00   $6.00  
  7 purchase totals = $696.77       $764.8044   $764.79   $764.80   $764.80