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 $61.75   5.153%   $64.932   $64.93   $64.95   $64.90  
  Purchase #2 $155.67   9.866%   $171.0284   $171.03   $171.05   $171.00  
  Purchase #3 $150.68   10.677%   $166.7681   $166.77   $166.75   $166.80  
  Purchase #4 $121.87   5.395%   $128.4449   $128.44   $128.45   $128.40  
  Purchase #5 $91.77   11.791%   $102.5906   $102.59   $102.60   $102.60  
  Purchase #6 $164.65   10.615%   $182.1276   $182.13   $182.15   $182.10  
  Purchase #7 $9.87   4.507%   $10.3148   $10.31   $10.30   $10.30  
  7 purchase totals = $756.26       $826.2064   $826.20   $826.25   $826.10