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 $43.93   6.421%   $46.7507   $46.75   $46.75   $46.80  
  Purchase #2 $234.70   12.374%   $263.7418   $263.74   $263.75   $263.70  
  Purchase #3 $200.52   11.106%   $222.7898   $222.79   $222.80   $222.80  
  Purchase #4 $164.70   4.179%   $171.5828   $171.58   $171.60   $171.60  
  Purchase #5 $162.97   13.481%   $184.94   $184.94   $184.95   $184.90  
  Purchase #6 $35.67   10.329%   $39.3544   $39.35   $39.35   $39.40  
  Purchase #7 $175.43   5.423%   $184.9436   $184.94   $184.95   $184.90  
  7 purchase totals = $1,017.92       $1,114.1031   $1,114.09   $1,114.15   $1,114.10