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 $156.42   12.658%   $176.2196   $176.22   $176.20   $176.20  
  Purchase #2 $80.48   8.657%   $87.4472   $87.45   $87.45   $87.40  
  Purchase #3 $176.74   11.786%   $197.5706   $197.57   $197.55   $197.60  
  Purchase #4 $52.54   10.616%   $58.1176   $58.12   $58.10   $58.10  
  Purchase #5 $91.49   6.203%   $97.1651   $97.17   $97.15   $97.20  
  Purchase #6 $208.78   8.250%   $226.0044   $226.00   $226.00   $226.00  
  Purchase #7 $241.25   9.634%   $264.492   $264.49   $264.50   $264.50  
  7 purchase totals = $1,007.70       $1,107.0165   $1,107.02   $1,106.95   $1,107.00