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 $58.32   4.640%   $61.026   $61.03   $61.05   $61.00  
  Purchase #2 $220.99   11.161%   $245.6547   $245.65   $245.65   $245.70  
  Purchase #3 $229.40   6.673%   $244.7079   $244.71   $244.70   $244.70  
  Purchase #4 $242.72   10.514%   $268.2396   $268.24   $268.25   $268.20  
  Purchase #5 $144.83   3.785%   $150.3118   $150.31   $150.30   $150.30  
  Purchase #6 $222.82   12.682%   $251.078   $251.08   $251.10   $251.10  
  Purchase #7 $85.51   9.783%   $93.8754   $93.88   $93.90   $93.90  
  7 purchase totals = $1,204.59       $1,314.8934   $1,314.90   $1,314.95   $1,314.90