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 $177.63   13.519%   $201.6438   $201.64   $201.65   $201.60  
  Purchase #2 $246.56   3.135%   $254.2897   $254.29   $254.30   $254.30  
  Purchase #3 $12.88   5.140%   $13.542   $13.54   $13.55   $13.50  
  Purchase #4 $191.83   4.671%   $200.7904   $200.79   $200.80   $200.80  
  Purchase #5 $237.44   6.617%   $253.1514   $253.15   $253.15   $253.20  
  Purchase #6 $72.28   3.568%   $74.859   $74.86   $74.85   $74.90  
  Purchase #7 $248.28   3.209%   $256.2473   $256.25   $256.25   $256.20  
  7 purchase totals = $1,186.90       $1,254.5236   $1,254.52   $1,254.55   $1,254.50