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 $151.72   6.760%   $161.9763   $161.98   $162.00   $162.00  
  Purchase #2 $163.65   5.780%   $173.109   $173.11   $173.10   $173.10  
  Purchase #3 $232.34   10.487%   $256.7055   $256.71   $256.70   $256.70  
  Purchase #4 $51.95   8.810%   $56.5268   $56.53   $56.55   $56.50  
  Purchase #5 $59.34   3.621%   $61.4887   $61.49   $61.50   $61.50  
  Purchase #6 $194.64   11.733%   $217.4771   $217.48   $217.50   $217.50  
  Purchase #7 $82.79   5.639%   $87.4585   $87.46   $87.45   $87.50  
  7 purchase totals = $936.43       $1,014.7419   $1,014.76   $1,014.80   $1,014.80