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 $179.42   9.163%   $195.8603   $195.86   $195.85   $195.90  
  Purchase #2 $198.54   12.174%   $222.7103   $222.71   $222.70   $222.70  
  Purchase #3 $26.61   10.314%   $29.3546   $29.35   $29.35   $29.40  
  Purchase #4 $16.93   3.227%   $17.4763   $17.48   $17.50   $17.50  
  Purchase #5 $51.84   11.449%   $57.7752   $57.78   $57.80   $57.80  
  Purchase #6 $151.64   9.823%   $166.5356   $166.54   $166.55   $166.50  
  Purchase #7 $200.90   5.299%   $211.5457   $211.55   $211.55   $211.50  
  7 purchase totals = $825.88       $901.2580   $901.27   $901.30   $901.30