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 $107.25   7.722%   $115.5318   $115.53   $115.55   $115.50  
  Purchase #2 $44.79   13.224%   $50.713   $50.71   $50.70   $50.70  
  Purchase #3 $218.81   5.375%   $230.571   $230.57   $230.55   $230.60  
  Purchase #4 $40.64   7.512%   $43.6929   $43.69   $43.70   $43.70  
  Purchase #5 $203.35   4.283%   $212.0595   $212.06   $212.05   $212.10  
  Purchase #6 $187.49   3.740%   $194.5021   $194.50   $194.50   $194.50  
  Purchase #7 $194.25   6.496%   $206.8685   $206.87   $206.85   $206.90  
  7 purchase totals = $996.58       $1,053.9388   $1,053.93   $1,053.90   $1,054.00