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 $32.69   9.133%   $35.6756   $35.68   $35.70   $35.70  
  Purchase #2 $126.41   9.236%   $138.0852   $138.09   $138.10   $138.10  
  Purchase #3 $151.76   9.140%   $165.6309   $165.63   $165.65   $165.60  
  Purchase #4 $217.27   10.493%   $240.0681   $240.07   $240.05   $240.10  
  Purchase #5 $80.75   13.803%   $91.8959   $91.90   $91.90   $91.90  
  Purchase #6 $208.92   11.775%   $233.5203   $233.52   $233.50   $233.50  
  Purchase #7 $102.70   3.239%   $106.0265   $106.03   $106.05   $106.00  
  7 purchase totals = $920.50       $1,010.9025   $1,010.92   $1,010.95   $1,010.90