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 $62.75   6.703%   $66.9561   $66.96   $66.95   $67.00  
  Purchase #2 $226.94   6.813%   $242.4014   $242.40   $242.40   $242.40  
  Purchase #3 $206.81   5.851%   $218.9105   $218.91   $218.90   $218.90  
  Purchase #4 $55.98   12.861%   $63.1796   $63.18   $63.20   $63.20  
  Purchase #5 $221.54   12.178%   $248.5191   $248.52   $248.50   $248.50  
  Purchase #6 $62.44   8.642%   $67.8361   $67.84   $67.85   $67.80  
  Purchase #7 $204.88   6.744%   $218.6971   $218.70   $218.70   $218.70  
  7 purchase totals = $1,041.34       $1,126.4999   $1,126.51   $1,126.50   $1,126.50