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 $69.44   7.551%   $74.6834   $74.68   $74.70   $74.70  
  Purchase #2 $120.92   11.230%   $134.4993   $134.50   $134.50   $134.50  
  Purchase #3 $52.74   12.544%   $59.3557   $59.36   $59.35   $59.40  
  Purchase #4 $86.51   8.636%   $93.981   $93.98   $94.00   $94.00  
  Purchase #5 $23.99   9.693%   $26.3154   $26.32   $26.30   $26.30  
  Purchase #6 $214.91   6.501%   $228.8813   $228.88   $228.90   $228.90  
  Purchase #7 $136.27   4.718%   $142.6992   $142.70   $142.70   $142.70  
  7 purchase totals = $704.78       $760.4153   $760.42   $760.45   $760.50