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 $176.81   9.164%   $193.0129   $193.01   $193.00   $193.00  
  Purchase #2 $186.78   4.693%   $195.5456   $195.55   $195.55   $195.50  
  Purchase #3 $142.31   9.596%   $155.9661   $155.97   $155.95   $156.00  
  Purchase #4 $192.90   5.833%   $204.1519   $204.15   $204.15   $204.20  
  Purchase #5 $152.94   5.116%   $160.7644   $160.76   $160.75   $160.80  
  Purchase #6 $9.52   7.628%   $10.2462   $10.25   $10.25   $10.20  
  Purchase #7 $109.76   13.312%   $124.3713   $124.37   $124.35   $124.40  
  7 purchase totals = $971.02       $1,044.0584   $1,044.06   $1,044.00   $1,044.10