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 $105.52   8.758%   $114.7614   $114.76   $114.75   $114.80  
  Purchase #2 $215.44   11.809%   $240.8813   $240.88   $240.90   $240.90  
  Purchase #3 $208.70   4.670%   $218.4463   $218.45   $218.45   $218.40  
  Purchase #4 $157.59   5.173%   $165.7421   $165.74   $165.75   $165.70  
  Purchase #5 $15.57   8.701%   $16.9247   $16.92   $16.90   $16.90  
  Purchase #6 $106.28   3.496%   $109.9955   $110.00   $110.00   $110.00  
  Purchase #7 $226.34   12.323%   $254.2319   $254.23   $254.25   $254.20  
  7 purchase totals = $1,035.44       $1,120.9832   $1,120.98   $1,121.00   $1,120.90