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 $118.86   8.702%   $129.2032   $129.20   $129.20   $129.20  
  Purchase #2 $181.41   6.287%   $192.8152   $192.82   $192.80   $192.80  
  Purchase #3 $110.87   5.284%   $116.7284   $116.73   $116.75   $116.70  
  Purchase #4 $61.78   7.347%   $66.319   $66.32   $66.30   $66.30  
  Purchase #5 $117.50   7.241%   $126.0082   $126.01   $126.00   $126.00  
  Purchase #6 $250.97   7.624%   $270.104   $270.10   $270.10   $270.10  
  Purchase #7 $177.96   12.844%   $200.8172   $200.82   $200.80   $200.80  
  7 purchase totals = $1,019.35       $1,101.9952   $1,102.00   $1,101.95   $1,101.90