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 $210.41   11.220%   $234.018   $234.02   $234.00   $234.00  
  Purchase #2 $98.40   13.403%   $111.5886   $111.59   $111.60   $111.60  
  Purchase #3 $144.50   4.127%   $150.4635   $150.46   $150.45   $150.50  
  Purchase #4 $182.25   13.592%   $207.0214   $207.02   $207.00   $207.00  
  Purchase #5 $192.77   5.770%   $203.8928   $203.89   $203.90   $203.90  
  Purchase #6 $240.46   9.691%   $263.763   $263.76   $263.75   $263.80  
  Purchase #7 $194.92   13.256%   $220.7586   $220.76   $220.75   $220.80  
  7 purchase totals = $1,263.71       $1,391.5059   $1,391.50   $1,391.45   $1,391.60