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 $86.98   8.533%   $94.402   $94.40   $94.40   $94.40  
  Purchase #2 $120.76   8.623%   $131.1731   $131.17   $131.15   $131.20  
  Purchase #3 $189.96   7.205%   $203.6466   $203.65   $203.65   $203.60  
  Purchase #4 $46.41   3.630%   $48.0947   $48.09   $48.10   $48.10  
  Purchase #5 $169.47   3.201%   $174.8947   $174.89   $174.90   $174.90  
  Purchase #6 $37.51   7.398%   $40.285   $40.29   $40.30   $40.30  
  Purchase #7 $62.98   7.414%   $67.6493   $67.65   $67.65   $67.60  
  7 purchase totals = $714.07       $760.1454   $760.14   $760.15   $760.10