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 $219.69   3.659%   $227.7285   $227.73   $227.75   $227.70  
  Purchase #2 $214.57   9.216%   $234.3448   $234.34   $234.35   $234.30  
  Purchase #3 $106.29   9.744%   $116.6469   $116.65   $116.65   $116.60  
  Purchase #4 $246.81   5.655%   $260.7671   $260.77   $260.75   $260.80  
  Purchase #5 $234.92   5.541%   $247.9369   $247.94   $247.95   $247.90  
  Purchase #6 $67.37   3.866%   $69.9745   $69.97   $69.95   $70.00  
  Purchase #7 $174.31   5.702%   $184.2492   $184.25   $184.25   $184.20  
  7 purchase totals = $1,263.96       $1,341.6479   $1,341.65   $1,341.65   $1,341.50