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 $194.41   5.708%   $205.5069   $205.51   $205.50   $205.50  
  Purchase #2 $16.36   6.144%   $17.3652   $17.37   $17.35   $17.40  
  Purchase #3 $15.92   4.175%   $16.5847   $16.58   $16.60   $16.60  
  Purchase #4 $101.54   3.309%   $104.9   $104.90   $104.90   $104.90  
  Purchase #5 $193.64   12.173%   $217.2118   $217.21   $217.20   $217.20  
  Purchase #6 $5.91   9.208%   $6.4542   $6.45   $6.45   $6.50  
  Purchase #7 $179.75   6.794%   $191.9622   $191.96   $191.95   $192.00  
  7 purchase totals = $707.53       $759.9850   $759.98   $759.95   $760.10