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 $184.83   4.681%   $193.4819   $193.48   $193.50   $193.50  
  Purchase #2 $215.87   13.350%   $244.6886   $244.69   $244.70   $244.70  
  Purchase #3 $11.91   4.336%   $12.4264   $12.43   $12.45   $12.40  
  Purchase #4 $40.50   10.638%   $44.8084   $44.81   $44.80   $44.80  
  Purchase #5 $232.65   4.313%   $242.6842   $242.68   $242.70   $242.70  
  Purchase #6 $39.50   4.294%   $41.1961   $41.20   $41.20   $41.20  
  Purchase #7 $49.27   9.182%   $53.794   $53.79   $53.80   $53.80  
  7 purchase totals = $774.53       $833.0796   $833.08   $833.15   $833.10