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 $45.54   6.767%   $48.6217   $48.62   $48.60   $48.60  
  Purchase #2 $103.82   5.790%   $109.8312   $109.83   $109.85   $109.80  
  Purchase #3 $213.26   6.471%   $227.0601   $227.06   $227.05   $227.10  
  Purchase #4 $12.79   11.556%   $14.268   $14.27   $14.25   $14.30  
  Purchase #5 $205.85   9.814%   $226.0521   $226.05   $226.05   $226.10  
  Purchase #6 $226.85   4.648%   $237.394   $237.39   $237.40   $237.40  
  Purchase #7 $73.83   5.196%   $77.6662   $77.67   $77.65   $77.70  
  7 purchase totals = $881.94       $940.8933   $940.89   $940.85   $941.00