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 $216.36   11.351%   $240.919   $240.92   $240.90   $240.90  
  Purchase #2 $226.55   12.204%   $254.1982   $254.20   $254.20   $254.20  
  Purchase #3 $17.93   9.790%   $19.6853   $19.69   $19.70   $19.70  
  Purchase #4 $68.84   7.821%   $74.224   $74.22   $74.20   $74.20  
  Purchase #5 $193.78   6.480%   $206.3369   $206.34   $206.35   $206.30  
  Purchase #6 $105.89   9.593%   $116.048   $116.05   $116.05   $116.00  
  Purchase #7 $234.41   3.260%   $242.0518   $242.05   $242.05   $242.10  
  7 purchase totals = $1,063.76       $1,153.4632   $1,153.47   $1,153.45   $1,153.40