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 $194.76   6.280%   $206.9909   $206.99   $207.00   $207.00  
  Purchase #2 $229.47   3.156%   $236.7121   $236.71   $236.70   $236.70  
  Purchase #3 $56.38   7.464%   $60.5882   $60.59   $60.60   $60.60  
  Purchase #4 $189.34   10.199%   $208.6508   $208.65   $208.65   $208.70  
  Purchase #5 $77.37   10.776%   $85.7074   $85.71   $85.70   $85.70  
  Purchase #6 $219.86   3.568%   $227.7046   $227.70   $227.70   $227.70  
  Purchase #7 $160.91   8.232%   $174.1561   $174.16   $174.15   $174.20  
  7 purchase totals = $1,128.09       $1,200.5101   $1,200.51   $1,200.50   $1,200.60