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 $86.90   8.448%   $94.2413   $94.24   $94.25   $94.20  
  Purchase #2 $234.71   5.808%   $248.342   $248.34   $248.35   $248.30  
  Purchase #3 $32.40   7.787%   $34.923   $34.92   $34.90   $34.90  
  Purchase #4 $243.99   9.531%   $267.2447   $267.24   $267.25   $267.20  
  Purchase #5 $193.35   13.271%   $219.0095   $219.01   $219.00   $219.00  
  Purchase #6 $10.32   8.488%   $11.196   $11.20   $11.20   $11.20  
  Purchase #7 $244.52   9.353%   $267.39   $267.39   $267.40   $267.40  
  7 purchase totals = $1,046.19       $1,142.3465   $1,142.34   $1,142.35   $1,142.20