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 $109.42   4.228%   $114.0463   $114.05   $114.05   $114.00  
  Purchase #2 $161.41   5.684%   $170.5845   $170.58   $170.60   $170.60  
  Purchase #3 $155.39   4.444%   $162.2955   $162.30   $162.30   $162.30  
  Purchase #4 $237.25   11.304%   $264.0687   $264.07   $264.05   $264.10  
  Purchase #5 $94.79   6.761%   $101.1988   $101.20   $101.20   $101.20  
  Purchase #6 $23.65   9.507%   $25.8984   $25.90   $25.90   $25.90  
  Purchase #7 $197.70   8.291%   $214.0913   $214.09   $214.10   $214.10  
  7 purchase totals = $979.61       $1,052.1835   $1,052.19   $1,052.20   $1,052.20