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 $120.95   5.578%   $127.6966   $127.70   $127.70   $127.70  
  Purchase #2 $125.40   10.197%   $138.187   $138.19   $138.20   $138.20  
  Purchase #3 $93.76   4.125%   $97.6276   $97.63   $97.65   $97.60  
  Purchase #4 $50.48   7.569%   $54.3008   $54.30   $54.30   $54.30  
  Purchase #5 $226.84   4.340%   $236.6849   $236.68   $236.70   $236.70  
  Purchase #6 $249.32   5.585%   $263.2445   $263.24   $263.25   $263.20  
  Purchase #7 $135.49   11.337%   $150.8505   $150.85   $150.85   $150.90  
  7 purchase totals = $1,002.24       $1,068.5919   $1,068.59   $1,068.65   $1,068.60