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 $52.63   10.617%   $58.2177   $58.22   $58.20   $58.20  
  Purchase #2 $204.95   9.360%   $224.1333   $224.13   $224.15   $224.10  
  Purchase #3 $202.87   6.839%   $216.7443   $216.74   $216.75   $216.70  
  Purchase #4 $183.36   9.149%   $200.1356   $200.14   $200.15   $200.10  
  Purchase #5 $216.73   8.661%   $235.501   $235.50   $235.50   $235.50  
  Purchase #6 $60.59   7.450%   $65.104   $65.10   $65.10   $65.10  
  Purchase #7 $142.96   6.584%   $152.3725   $152.37   $152.35   $152.40  
  7 purchase totals = $1,064.09       $1,152.2084   $1,152.20   $1,152.20   $1,152.10