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 $41.67   3.267%   $43.0314   $43.03   $43.05   $43.00  
  Purchase #2 $100.36   11.203%   $111.6033   $111.60   $111.60   $111.60  
  Purchase #3 $166.73   10.438%   $184.1333   $184.13   $184.15   $184.10  
  Purchase #4 $235.81   4.410%   $246.2092   $246.21   $246.20   $246.20  
  Purchase #5 $210.67   5.175%   $221.5722   $221.57   $221.55   $221.60  
  Purchase #6 $178.64   5.534%   $188.5259   $188.53   $188.55   $188.50  
  Purchase #7 $11.84   9.426%   $12.956   $12.96   $12.95   $13.00  
  7 purchase totals = $945.72       $1,008.0313   $1,008.03   $1,008.05   $1,008.00