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 $95.32   3.297%   $98.4627   $98.46   $98.45   $98.50  
  Purchase #2 $49.93   10.146%   $54.9959   $55.00   $55.00   $55.00  
  Purchase #3 $33.82   9.542%   $37.0471   $37.05   $37.05   $37.00  
  Purchase #4 $204.62   7.482%   $219.9297   $219.93   $219.95   $219.90  
  Purchase #5 $210.78   11.521%   $235.064   $235.06   $235.05   $235.10  
  Purchase #6 $37.54   9.642%   $41.1596   $41.16   $41.15   $41.20  
  Purchase #7 $105.40   6.872%   $112.6431   $112.64   $112.65   $112.60  
  7 purchase totals = $737.41       $799.3021   $799.30   $799.30   $799.30