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 $205.50   10.627%   $227.3385   $227.34   $227.35   $227.30  
  Purchase #2 $222.79   5.323%   $234.6491   $234.65   $234.65   $234.60  
  Purchase #3 $35.98   5.561%   $37.9808   $37.98   $38.00   $38.00  
  Purchase #4 $41.96   9.505%   $45.9483   $45.95   $45.95   $45.90  
  Purchase #5 $50.48   13.243%   $57.1651   $57.17   $57.15   $57.20  
  Purchase #6 $121.95   9.763%   $133.856   $133.86   $133.85   $133.90  
  Purchase #7 $184.27   8.809%   $200.5023   $200.50   $200.50   $200.50  
  7 purchase totals = $862.93       $937.4401   $937.45   $937.45   $937.40