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 $57.96   4.699%   $60.6835   $60.68   $60.70   $60.70  
  Purchase #2 $99.50   6.784%   $106.2501   $106.25   $106.25   $106.30  
  Purchase #3 $245.84   6.851%   $262.6825   $262.68   $262.70   $262.70  
  Purchase #4 $137.98   6.170%   $146.4934   $146.49   $146.50   $146.50  
  Purchase #5 $65.40   4.573%   $68.3907   $68.39   $68.40   $68.40  
  Purchase #6 $46.25   13.814%   $52.639   $52.64   $52.65   $52.60  
  Purchase #7 $241.65   4.229%   $251.8694   $251.87   $251.85   $251.90  
  7 purchase totals = $894.58       $949.0086   $949.00   $949.05   $949.10