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 $72.94   5.472%   $76.9313   $76.93   $76.95   $76.90  
  Purchase #2 $148.79   8.626%   $161.6246   $161.62   $161.60   $161.60  
  Purchase #3 $218.83   6.525%   $233.1087   $233.11   $233.10   $233.10  
  Purchase #4 $215.55   5.284%   $226.9397   $226.94   $226.95   $226.90  
  Purchase #5 $65.81   13.459%   $74.6674   $74.67   $74.65   $74.70  
  Purchase #6 $97.71   8.785%   $106.2938   $106.29   $106.30   $106.30  
  Purchase #7 $122.52   6.816%   $130.871   $130.87   $130.85   $130.90  
  7 purchase totals = $942.15       $1,010.4365   $1,010.43   $1,010.40   $1,010.40