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 $211.86   10.457%   $234.0142   $234.01   $234.00   $234.00  
  Purchase #2 $118.94   11.535%   $132.6597   $132.66   $132.65   $132.70  
  Purchase #3 $80.85   5.819%   $85.5547   $85.55   $85.55   $85.60  
  Purchase #4 $133.69   8.742%   $145.3772   $145.38   $145.40   $145.40  
  Purchase #5 $197.52   6.492%   $210.343   $210.34   $210.35   $210.30  
  Purchase #6 $121.93   12.143%   $136.736   $136.74   $136.75   $136.70  
  Purchase #7 $146.93   11.141%   $163.2995   $163.30   $163.30   $163.30  
  7 purchase totals = $1,011.72       $1,107.9843   $1,107.98   $1,108.00   $1,108.00