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 $70.35   8.217%   $76.1307   $76.13   $76.15   $76.10  
  Purchase #2 $201.98   6.277%   $214.6583   $214.66   $214.65   $214.70  
  Purchase #3 $10.76   6.316%   $11.4396   $11.44   $11.45   $11.40  
  Purchase #4 $96.78   6.662%   $103.2275   $103.23   $103.25   $103.20  
  Purchase #5 $193.26   9.179%   $210.9993   $211.00   $211.00   $211.00  
  Purchase #6 $212.38   3.469%   $219.7475   $219.75   $219.75   $219.70  
  Purchase #7 $116.78   9.664%   $128.0656   $128.07   $128.05   $128.10  
  7 purchase totals = $902.29       $964.2685   $964.28   $964.30   $964.20