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 $158.71   11.367%   $176.7506   $176.75   $176.75   $176.80  
  Purchase #2 $192.97   7.855%   $208.1278   $208.13   $208.15   $208.10  
  Purchase #3 $218.98   9.649%   $240.1094   $240.11   $240.10   $240.10  
  Purchase #4 $228.95   5.560%   $241.6796   $241.68   $241.70   $241.70  
  Purchase #5 $119.44   6.294%   $126.9576   $126.96   $126.95   $127.00  
  Purchase #6 $102.32   11.333%   $113.9159   $113.92   $113.90   $113.90  
  Purchase #7 $11.52   4.592%   $12.049   $12.05   $12.05   $12.00  
  7 purchase totals = $1,032.89       $1,119.5899   $1,119.60   $1,119.60   $1,119.60