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 $98.25   8.526%   $106.6268   $106.63   $106.65   $106.60  
  Purchase #2 $46.55   13.795%   $52.9716   $52.97   $52.95   $53.00  
  Purchase #3 $178.86   12.570%   $201.3427   $201.34   $201.35   $201.30  
  Purchase #4 $68.66   8.645%   $74.5957   $74.60   $74.60   $74.60  
  Purchase #5 $191.97   12.244%   $215.4748   $215.47   $215.45   $215.50  
  Purchase #6 $204.91   6.391%   $218.0058   $218.01   $218.00   $218.00  
  Purchase #7 $164.85   6.324%   $175.2751   $175.28   $175.30   $175.30  
  7 purchase totals = $954.05       $1,044.2925   $1,044.30   $1,044.30   $1,044.30