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 $182.65   4.599%   $191.0501   $191.05   $191.05   $191.10  
  Purchase #2 $213.73   3.571%   $221.3623   $221.36   $221.35   $221.40  
  Purchase #3 $172.34   10.527%   $190.4822   $190.48   $190.50   $190.50  
  Purchase #4 $155.65   8.692%   $169.1791   $169.18   $169.20   $169.20  
  Purchase #5 $245.88   6.589%   $262.081   $262.08   $262.10   $262.10  
  Purchase #6 $202.40   11.520%   $225.7165   $225.72   $225.70   $225.70  
  Purchase #7 $211.28   5.794%   $223.5216   $223.52   $223.50   $223.50  
  7 purchase totals = $1,383.93       $1,483.3928   $1,483.39   $1,483.40   $1,483.50