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 $60.96   3.865%   $63.3161   $63.32   $63.30   $63.30  
  Purchase #2 $119.42   10.835%   $132.3592   $132.36   $132.35   $132.40  
  Purchase #3 $47.42   3.642%   $49.147   $49.15   $49.15   $49.10  
  Purchase #4 $60.68   4.677%   $63.518   $63.52   $63.50   $63.50  
  Purchase #5 $93.98   13.258%   $106.4399   $106.44   $106.45   $106.40  
  Purchase #6 $91.93   7.479%   $98.8054   $98.81   $98.80   $98.80  
  Purchase #7 $202.43   5.631%   $213.8288   $213.83   $213.85   $213.80  
  7 purchase totals = $676.82       $727.4144   $727.43   $727.40   $727.30