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 $216.98   11.366%   $241.6419   $241.64   $241.65   $241.60  
  Purchase #2 $168.62   4.432%   $176.0932   $176.09   $176.10   $176.10  
  Purchase #3 $45.41   12.257%   $50.9759   $50.98   $51.00   $51.00  
  Purchase #4 $187.31   3.820%   $194.4652   $194.47   $194.45   $194.50  
  Purchase #5 $123.94   13.629%   $140.8318   $140.83   $140.85   $140.80  
  Purchase #6 $107.89   12.381%   $121.2479   $121.25   $121.25   $121.20  
  Purchase #7 $104.99   6.554%   $111.871   $111.87   $111.85   $111.90  
  7 purchase totals = $955.14       $1,037.1269   $1,037.13   $1,037.15   $1,037.10