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 $186.51   8.150%   $201.7106   $201.71   $201.70   $201.70  
  Purchase #2 $176.52   6.816%   $188.5516   $188.55   $188.55   $188.60  
  Purchase #3 $69.35   6.638%   $73.9535   $73.95   $73.95   $74.00  
  Purchase #4 $55.87   8.588%   $60.6681   $60.67   $60.65   $60.70  
  Purchase #5 $163.25   11.704%   $182.3568   $182.36   $182.35   $182.40  
  Purchase #6 $187.54   8.788%   $204.021   $204.02   $204.00   $204.00  
  Purchase #7 $248.34   9.209%   $271.2096   $271.21   $271.20   $271.20  
  7 purchase totals = $1,087.38       $1,182.4712   $1,182.47   $1,182.40   $1,182.60