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 $211.96   6.317%   $225.3495   $225.35   $225.35   $225.30  
  Purchase #2 $62.92   8.440%   $68.2304   $68.23   $68.25   $68.20  
  Purchase #3 $143.55   8.594%   $155.8867   $155.89   $155.90   $155.90  
  Purchase #4 $161.37   9.212%   $176.2354   $176.24   $176.25   $176.20  
  Purchase #5 $206.91   9.134%   $225.8092   $225.81   $225.80   $225.80  
  Purchase #6 $98.92   5.833%   $104.69   $104.69   $104.70   $104.70  
  Purchase #7 $180.26   12.108%   $202.0859   $202.09   $202.10   $202.10  
  7 purchase totals = $1,065.89       $1,158.2871   $1,158.30   $1,158.35   $1,158.20