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 $41.33   4.767%   $43.3002   $43.30   $43.30   $43.30  
  Purchase #2 $180.53   6.432%   $192.1417   $192.14   $192.15   $192.10  
  Purchase #3 $201.34   4.795%   $210.9943   $210.99   $211.00   $211.00  
  Purchase #4 $163.34   5.442%   $172.229   $172.23   $172.25   $172.20  
  Purchase #5 $245.70   8.128%   $265.6705   $265.67   $265.65   $265.70  
  Purchase #6 $41.94   3.818%   $43.5413   $43.54   $43.55   $43.50  
  Purchase #7 $168.44   3.414%   $174.1905   $174.19   $174.20   $174.20  
  7 purchase totals = $1,042.62       $1,102.0675   $1,102.06   $1,102.10   $1,102.00