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 $168.81   5.237%   $177.6506   $177.65   $177.65   $177.70  
  Purchase #2 $214.97   4.451%   $224.5383   $224.54   $224.55   $224.50  
  Purchase #3 $238.85   13.135%   $270.2229   $270.22   $270.20   $270.20  
  Purchase #4 $94.90   9.121%   $103.5558   $103.56   $103.55   $103.60  
  Purchase #5 $169.87   12.289%   $190.7453   $190.75   $190.75   $190.70  
  Purchase #6 $238.92   5.424%   $251.879   $251.88   $251.90   $251.90  
  Purchase #7 $227.52   4.204%   $237.0849   $237.08   $237.10   $237.10  
  7 purchase totals = $1,353.84       $1,455.6768   $1,455.68   $1,455.70   $1,455.70