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 $60.58   13.254%   $68.6093   $68.61   $68.60   $68.60  
  Purchase #2 $176.42   10.377%   $194.7271   $194.73   $194.75   $194.70  
  Purchase #3 $208.58   5.422%   $219.8892   $219.89   $219.90   $219.90  
  Purchase #4 $232.79   3.654%   $241.2961   $241.30   $241.30   $241.30  
  Purchase #5 $166.82   12.570%   $187.7893   $187.79   $187.80   $187.80  
  Purchase #6 $10.86   3.564%   $11.2471   $11.25   $11.25   $11.20  
  Purchase #7 $197.90   12.382%   $222.404   $222.40   $222.40   $222.40  
  7 purchase totals = $1,053.95       $1,145.9621   $1,145.97   $1,146.00   $1,145.90