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 $111.85   13.553%   $127.009   $127.01   $127.00   $127.00  
  Purchase #2 $244.52   9.602%   $267.9988   $268.00   $268.00   $268.00  
  Purchase #3 $165.86   5.107%   $174.3305   $174.33   $174.35   $174.30  
  Purchase #4 $76.30   6.630%   $81.3587   $81.36   $81.35   $81.40  
  Purchase #5 $61.69   11.228%   $68.6166   $68.62   $68.60   $68.60  
  Purchase #6 $182.77   11.691%   $204.1376   $204.14   $204.15   $204.10  
  Purchase #7 $238.97   9.680%   $262.1023   $262.10   $262.10   $262.10  
  7 purchase totals = $1,081.96       $1,185.5535   $1,185.56   $1,185.55   $1,185.50