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 $211.94   11.180%   $235.6349   $235.63   $235.65   $235.60  
  Purchase #2 $244.87   12.331%   $275.0649   $275.06   $275.05   $275.10  
  Purchase #3 $72.74   13.808%   $82.7839   $82.78   $82.80   $82.80  
  Purchase #4 $57.26   8.121%   $61.9101   $61.91   $61.90   $61.90  
  Purchase #5 $163.80   12.353%   $184.0342   $184.03   $184.05   $184.00  
  Purchase #6 $153.36   4.478%   $160.2275   $160.23   $160.25   $160.20  
  Purchase #7 $188.58   11.288%   $209.8669   $209.87   $209.85   $209.90  
  7 purchase totals = $1,092.55       $1,209.5224   $1,209.51   $1,209.55   $1,209.50