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 $153.36   9.852%   $168.469   $168.47   $168.45   $168.50  
  Purchase #2 $208.53   8.535%   $226.328   $226.33   $226.35   $226.30  
  Purchase #3 $96.61   11.771%   $107.982   $107.98   $108.00   $108.00  
  Purchase #4 $60.29   3.597%   $62.4586   $62.46   $62.45   $62.50  
  Purchase #5 $62.87   4.843%   $65.9148   $65.91   $65.90   $65.90  
  Purchase #6 $241.35   12.776%   $272.1849   $272.18   $272.20   $272.20  
  Purchase #7 $61.64   3.392%   $63.7308   $63.73   $63.75   $63.70  
  7 purchase totals = $884.65       $967.0681   $967.06   $967.10   $967.10