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 $212.46   9.486%   $232.614   $232.61   $232.60   $232.60  
  Purchase #2 $149.58   8.201%   $161.8471   $161.85   $161.85   $161.80  
  Purchase #3 $14.27   4.215%   $14.8715   $14.87   $14.85   $14.90  
  Purchase #4 $127.29   7.355%   $136.6522   $136.65   $136.65   $136.70  
  Purchase #5 $167.80   11.839%   $187.6658   $187.67   $187.65   $187.70  
  Purchase #6 $109.71   3.487%   $113.5356   $113.54   $113.55   $113.50  
  Purchase #7 $26.49   11.294%   $29.4818   $29.48   $29.50   $29.50  
  7 purchase totals = $807.60       $876.6680   $876.67   $876.65   $876.70