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 $216.26   8.224%   $234.0452   $234.05   $234.05   $234.00  
  Purchase #2 $196.31   12.585%   $221.0156   $221.02   $221.00   $221.00  
  Purchase #3 $208.28   12.575%   $234.4712   $234.47   $234.45   $234.50  
  Purchase #4 $40.95   9.311%   $44.7629   $44.76   $44.75   $44.80  
  Purchase #5 $68.48   8.144%   $74.057   $74.06   $74.05   $74.10  
  Purchase #6 $217.47   5.559%   $229.5592   $229.56   $229.55   $229.60  
  Purchase #7 $57.30   4.459%   $59.855   $59.86   $59.85   $59.90  
  7 purchase totals = $1,005.05       $1,097.7661   $1,097.78   $1,097.70   $1,097.90