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 $146.55   3.513%   $151.6983   $151.70   $151.70   $151.70  
  Purchase #2 $192.51   5.855%   $203.7815   $203.78   $203.80   $203.80  
  Purchase #3 $192.79   9.439%   $210.9874   $210.99   $211.00   $211.00  
  Purchase #4 $85.87   11.265%   $95.5433   $95.54   $95.55   $95.50  
  Purchase #5 $82.74   9.571%   $90.659   $90.66   $90.65   $90.70  
  Purchase #6 $178.89   4.569%   $187.0635   $187.06   $187.05   $187.10  
  Purchase #7 $216.41   8.559%   $234.9325   $234.93   $234.95   $234.90  
  7 purchase totals = $1,095.76       $1,174.6655   $1,174.66   $1,174.70   $1,174.70