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 $62.95   9.855%   $69.1537   $69.15   $69.15   $69.20  
  Purchase #2 $229.75   7.677%   $247.3879   $247.39   $247.40   $247.40  
  Purchase #3 $166.48   7.834%   $179.522   $179.52   $179.50   $179.50  
  Purchase #4 $196.82   11.580%   $219.6118   $219.61   $219.60   $219.60  
  Purchase #5 $110.73   8.659%   $120.3181   $120.32   $120.30   $120.30  
  Purchase #6 $31.62   11.438%   $35.2367   $35.24   $35.25   $35.20  
  Purchase #7 $216.33   3.730%   $224.3991   $224.40   $224.40   $224.40  
  7 purchase totals = $1,014.68       $1,095.6293   $1,095.63   $1,095.60   $1,095.60