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 $92.53   3.141%   $95.4364   $95.44   $95.45   $95.40  
  Purchase #2 $53.50   4.304%   $55.8026   $55.80   $55.80   $55.80  
  Purchase #3 $205.67   13.209%   $232.837   $232.84   $232.85   $232.80  
  Purchase #4 $19.47   8.592%   $21.1429   $21.14   $21.15   $21.10  
  Purchase #5 $141.29   10.305%   $155.8499   $155.85   $155.85   $155.80  
  Purchase #6 $235.61   11.770%   $263.3413   $263.34   $263.35   $263.30  
  Purchase #7 $8.36   3.771%   $8.6753   $8.68   $8.70   $8.70  
  7 purchase totals = $756.43       $833.0854   $833.09   $833.15   $832.90