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 $86.93   7.709%   $93.6314   $93.63   $93.65   $93.60  
  Purchase #2 $141.67   7.423%   $152.1862   $152.19   $152.20   $152.20  
  Purchase #3 $216.47   10.525%   $239.2535   $239.25   $239.25   $239.30  
  Purchase #4 $229.66   6.719%   $245.0909   $245.09   $245.10   $245.10  
  Purchase #5 $245.87   3.564%   $254.6328   $254.63   $254.65   $254.60  
  Purchase #6 $233.74   3.310%   $241.4768   $241.48   $241.50   $241.50  
  Purchase #7 $128.71   7.451%   $138.3002   $138.30   $138.30   $138.30  
  7 purchase totals = $1,283.05       $1,364.5718   $1,364.57   $1,364.65   $1,364.60