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 $119.32   4.776%   $125.0187   $125.02   $125.00   $125.00  
  Purchase #2 $169.49   5.492%   $178.7984   $178.80   $178.80   $178.80  
  Purchase #3 $97.93   9.172%   $106.9121   $106.91   $106.90   $106.90  
  Purchase #4 $35.37   12.257%   $39.7053   $39.71   $39.70   $39.70  
  Purchase #5 $29.60   8.687%   $32.1714   $32.17   $32.15   $32.20  
  Purchase #6 $207.44   7.722%   $223.4585   $223.46   $223.45   $223.50  
  Purchase #7 $46.99   11.313%   $52.306   $52.31   $52.30   $52.30  
  7 purchase totals = $706.14       $758.3704   $758.38   $758.30   $758.40