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 $45.60   6.713%   $48.6611   $48.66   $48.65   $48.70  
  Purchase #2 $239.97   5.805%   $253.9003   $253.90   $253.90   $253.90  
  Purchase #3 $181.69   5.339%   $191.3904   $191.39   $191.40   $191.40  
  Purchase #4 $17.47   11.838%   $19.5381   $19.54   $19.55   $19.50  
  Purchase #5 $70.33   10.675%   $77.8377   $77.84   $77.85   $77.80  
  Purchase #6 $196.30   3.318%   $202.8132   $202.81   $202.80   $202.80  
  Purchase #7 $204.76   7.392%   $219.8959   $219.90   $219.90   $219.90  
  7 purchase totals = $956.12       $1,014.0367   $1,014.04   $1,014.05   $1,014.00