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 $175.83   4.831%   $184.3243   $184.32   $184.30   $184.30  
  Purchase #2 $14.49   10.626%   $16.0297   $16.03   $16.05   $16.00  
  Purchase #3 $65.81   3.755%   $68.2812   $68.28   $68.30   $68.30  
  Purchase #4 $215.98   5.291%   $227.4075   $227.41   $227.40   $227.40  
  Purchase #5 $236.50   4.724%   $247.6723   $247.67   $247.65   $247.70  
  Purchase #6 $246.92   7.282%   $264.9007   $264.90   $264.90   $264.90  
  Purchase #7 $191.62   7.158%   $205.3362   $205.34   $205.35   $205.30  
  7 purchase totals = $1,147.15       $1,213.9519   $1,213.95   $1,213.95   $1,213.90