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 $86.43   10.625%   $95.6132   $95.61   $95.60   $95.60  
  Purchase #2 $234.48   8.313%   $253.9723   $253.97   $253.95   $254.00  
  Purchase #3 $151.94   7.654%   $163.5695   $163.57   $163.55   $163.60  
  Purchase #4 $244.80   12.145%   $274.531   $274.53   $274.55   $274.50  
  Purchase #5 $107.80   9.340%   $117.8685   $117.87   $117.85   $117.90  
  Purchase #6 $193.68   13.184%   $219.2148   $219.21   $219.20   $219.20  
  Purchase #7 $37.41   4.331%   $39.0302   $39.03   $39.05   $39.00  
  7 purchase totals = $1,056.54       $1,163.7995   $1,163.79   $1,163.75   $1,163.80