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 $106.43   5.563%   $112.3507   $112.35   $112.35   $112.40  
  Purchase #2 $41.39   9.564%   $45.3485   $45.35   $45.35   $45.30  
  Purchase #3 $155.95   12.149%   $174.8964   $174.90   $174.90   $174.90  
  Purchase #4 $205.96   6.102%   $218.5277   $218.53   $218.55   $218.50  
  Purchase #5 $68.92   12.627%   $77.6225   $77.62   $77.60   $77.60  
  Purchase #6 $87.45   8.557%   $94.9331   $94.93   $94.95   $94.90  
  Purchase #7 $132.63   4.800%   $138.9962   $139.00   $139.00   $139.00  
  7 purchase totals = $798.73       $862.6751   $862.68   $862.70   $862.60