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 $164.84   6.429%   $175.4376   $175.44   $175.45   $175.40  
  Purchase #2 $226.97   5.425%   $239.2831   $239.28   $239.30   $239.30  
  Purchase #3 $225.39   10.294%   $248.5916   $248.59   $248.60   $248.60  
  Purchase #4 $58.48   5.423%   $61.6514   $61.65   $61.65   $61.70  
  Purchase #5 $62.75   4.257%   $65.4213   $65.42   $65.40   $65.40  
  Purchase #6 $201.78   5.282%   $212.438   $212.44   $212.45   $212.40  
  Purchase #7 $128.30   10.252%   $141.4533   $141.45   $141.45   $141.50  
  7 purchase totals = $1,068.51       $1,144.2763   $1,144.27   $1,144.30   $1,144.30