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 $53.76   13.721%   $61.1364   $61.14   $61.15   $61.10  
  Purchase #2 $220.39   11.158%   $244.9811   $244.98   $245.00   $245.00  
  Purchase #3 $163.61   6.731%   $174.6226   $174.62   $174.60   $174.60  
  Purchase #4 $147.86   5.865%   $156.532   $156.53   $156.55   $156.50  
  Purchase #5 $237.45   3.458%   $245.661   $245.66   $245.65   $245.70  
  Purchase #6 $138.43   8.654%   $150.4097   $150.41   $150.40   $150.40  
  Purchase #7 $216.68   11.459%   $241.5094   $241.51   $241.50   $241.50  
  7 purchase totals = $1,178.18       $1,274.8522   $1,274.85   $1,274.85   $1,274.80