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 $91.70   4.386%   $95.722   $95.72   $95.70   $95.70  
  Purchase #2 $69.82   10.764%   $77.3354   $77.34   $77.35   $77.30  
  Purchase #3 $102.66   7.348%   $110.2035   $110.20   $110.20   $110.20  
  Purchase #4 $193.44   10.170%   $213.1128   $213.11   $213.10   $213.10  
  Purchase #5 $211.91   9.706%   $232.478   $232.48   $232.50   $232.50  
  Purchase #6 $171.81   3.193%   $177.2959   $177.30   $177.30   $177.30  
  Purchase #7 $241.27   9.784%   $264.8759   $264.88   $264.90   $264.90  
  7 purchase totals = $1,082.61       $1,171.0235   $1,171.03   $1,171.05   $1,171.00