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 $83.29   12.822%   $93.9694   $93.97   $93.95   $94.00  
  Purchase #2 $235.31   3.699%   $244.0141   $244.01   $244.00   $244.00  
  Purchase #3 $86.40   6.528%   $92.0402   $92.04   $92.05   $92.00  
  Purchase #4 $60.41   7.665%   $65.0404   $65.04   $65.05   $65.00  
  Purchase #5 $193.86   13.458%   $219.9497   $219.95   $219.95   $219.90  
  Purchase #6 $43.81   11.847%   $49.0002   $49.00   $49.00   $49.00  
  Purchase #7 $225.72   6.804%   $241.078   $241.08   $241.10   $241.10  
  7 purchase totals = $928.80       $1,005.0920   $1,005.09   $1,005.10   $1,005.00