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 $91.72   3.577%   $95.0008   $95.00   $95.00   $95.00  
  Purchase #2 $228.82   13.385%   $259.4476   $259.45   $259.45   $259.40  
  Purchase #3 $190.55   7.536%   $204.9098   $204.91   $204.90   $204.90  
  Purchase #4 $57.91   9.485%   $63.4028   $63.40   $63.40   $63.40  
  Purchase #5 $67.79   11.868%   $75.8353   $75.84   $75.85   $75.80  
  Purchase #6 $220.81   11.763%   $246.7839   $246.78   $246.80   $246.80  
  Purchase #7 $214.91   11.807%   $240.2844   $240.28   $240.30   $240.30  
  7 purchase totals = $1,072.51       $1,185.6646   $1,185.66   $1,185.70   $1,185.60