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 $214.58   5.727%   $226.869   $226.87   $226.85   $226.90  
  Purchase #2 $174.26   13.621%   $197.996   $198.00   $198.00   $198.00  
  Purchase #3 $66.73   4.178%   $69.518   $69.52   $69.50   $69.50  
  Purchase #4 $212.47   3.812%   $220.5694   $220.57   $220.55   $220.60  
  Purchase #5 $226.99   6.865%   $242.5729   $242.57   $242.55   $242.60  
  Purchase #6 $150.86   5.134%   $158.6052   $158.61   $158.60   $158.60  
  Purchase #7 $85.35   5.585%   $90.1168   $90.12   $90.10   $90.10  
  7 purchase totals = $1,131.24       $1,206.2473   $1,206.26   $1,206.15   $1,206.30