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 $56.41   5.745%   $59.6508   $59.65   $59.65   $59.70  
  Purchase #2 $214.59   6.406%   $228.3366   $228.34   $228.35   $228.30  
  Purchase #3 $60.89   10.179%   $67.088   $67.09   $67.10   $67.10  
  Purchase #4 $204.67   9.280%   $223.6634   $223.66   $223.65   $223.70  
  Purchase #5 $98.74   8.318%   $106.9532   $106.95   $106.95   $107.00  
  Purchase #6 $178.91   6.859%   $191.1814   $191.18   $191.20   $191.20  
  Purchase #7 $140.99   8.113%   $152.4285   $152.43   $152.45   $152.40  
  7 purchase totals = $955.20       $1,029.3019   $1,029.30   $1,029.35   $1,029.40