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 $57.88   7.394%   $62.1596   $62.16   $62.15   $62.20  
  Purchase #2 $224.99   6.107%   $238.7301   $238.73   $238.75   $238.70  
  Purchase #3 $59.43   8.524%   $64.4958   $64.50   $64.50   $64.50  
  Purchase #4 $51.36   8.424%   $55.6866   $55.69   $55.70   $55.70  
  Purchase #5 $217.31   4.149%   $226.3262   $226.33   $226.35   $226.30  
  Purchase #6 $153.37   11.320%   $170.7315   $170.73   $170.75   $170.70  
  Purchase #7 $179.33   9.224%   $195.8714   $195.87   $195.85   $195.90  
  7 purchase totals = $943.67       $1,014.0012   $1,014.01   $1,014.05   $1,014.00