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 $120.59   4.761%   $126.3313   $126.33   $126.35   $126.30  
  Purchase #2 $51.56   12.437%   $57.9725   $57.97   $57.95   $58.00  
  Purchase #3 $223.75   5.471%   $235.9914   $235.99   $236.00   $236.00  
  Purchase #4 $96.56   11.615%   $107.7754   $107.78   $107.80   $107.80  
  Purchase #5 $132.87   6.293%   $141.2315   $141.23   $141.25   $141.20  
  Purchase #6 $158.42   8.268%   $171.5182   $171.52   $171.50   $171.50  
  Purchase #7 $109.98   10.822%   $121.882   $121.88   $121.90   $121.90  
  7 purchase totals = $893.73       $962.7023   $962.70   $962.75   $962.70