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 $62.76   7.361%   $67.3798   $67.38   $67.40   $67.40  
  Purchase #2 $175.56   8.504%   $190.4896   $190.49   $190.50   $190.50  
  Purchase #3 $212.97   10.485%   $235.2999   $235.30   $235.30   $235.30  
  Purchase #4 $249.73   7.744%   $269.0691   $269.07   $269.05   $269.10  
  Purchase #5 $236.61   7.271%   $253.8139   $253.81   $253.80   $253.80  
  Purchase #6 $39.31   9.767%   $43.1494   $43.15   $43.15   $43.10  
  Purchase #7 $8.32   7.506%   $8.9445   $8.94   $8.95   $8.90  
  7 purchase totals = $985.26       $1,068.1462   $1,068.14   $1,068.15   $1,068.10