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 $186.44   8.331%   $201.9723   $201.97   $201.95   $202.00  
  Purchase #2 $55.33   8.355%   $59.9528   $59.95   $59.95   $60.00  
  Purchase #3 $221.70   13.258%   $251.093   $251.09   $251.10   $251.10  
  Purchase #4 $214.41   6.576%   $228.5096   $228.51   $228.50   $228.50  
  Purchase #5 $219.37   10.205%   $241.7567   $241.76   $241.75   $241.80  
  Purchase #6 $249.89   6.309%   $265.6556   $265.66   $265.65   $265.70  
  Purchase #7 $159.81   3.751%   $165.8045   $165.80   $165.80   $165.80  
  7 purchase totals = $1,306.95       $1,414.7445   $1,414.74   $1,414.70   $1,414.90