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 $37.52   10.711%   $41.5388   $41.54   $41.55   $41.50  
  Purchase #2 $223.74   11.735%   $249.9959   $250.00   $250.00   $250.00  
  Purchase #3 $207.57   10.482%   $229.3275   $229.33   $229.35   $229.30  
  Purchase #4 $205.79   3.235%   $212.4473   $212.45   $212.45   $212.40  
  Purchase #5 $58.54   13.823%   $66.632   $66.63   $66.65   $66.60  
  Purchase #6 $42.84   3.314%   $44.2597   $44.26   $44.25   $44.30  
  Purchase #7 $242.72   8.415%   $263.1449   $263.14   $263.15   $263.10  
  7 purchase totals = $1,018.72       $1,107.3461   $1,107.35   $1,107.40   $1,107.20