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 $44.33   4.350%   $46.2584   $46.26   $46.25   $46.30  
  Purchase #2 $219.92   4.588%   $230.0099   $230.01   $230.00   $230.00  
  Purchase #3 $226.43   11.121%   $251.6113   $251.61   $251.60   $251.60  
  Purchase #4 $53.93   6.716%   $57.5519   $57.55   $57.55   $57.60  
  Purchase #5 $182.39   10.692%   $201.8911   $201.89   $201.90   $201.90  
  Purchase #6 $144.30   4.284%   $150.4818   $150.48   $150.50   $150.50  
  Purchase #7 $122.94   6.294%   $130.6778   $130.68   $130.70   $130.70  
  7 purchase totals = $994.24       $1,068.4822   $1,068.48   $1,068.50   $1,068.60