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 $165.28   6.701%   $176.3554   $176.36   $176.35   $176.40  
  Purchase #2 $111.99   11.680%   $125.0704   $125.07   $125.05   $125.10  
  Purchase #3 $115.26   7.283%   $123.6544   $123.65   $123.65   $123.70  
  Purchase #4 $208.55   12.729%   $235.0963   $235.10   $235.10   $235.10  
  Purchase #5 $58.39   9.690%   $64.048   $64.05   $64.05   $64.00  
  Purchase #6 $110.83   9.515%   $121.3755   $121.38   $121.40   $121.40  
  Purchase #7 $227.73   9.493%   $249.3484   $249.35   $249.35   $249.30  
  7 purchase totals = $998.03       $1,094.9484   $1,094.96   $1,094.95   $1,095.00