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 $197.84   8.771%   $215.1925   $215.19   $215.20   $215.20  
  Purchase #2 $86.60   13.423%   $98.2243   $98.22   $98.20   $98.20  
  Purchase #3 $135.79   9.555%   $148.7647   $148.76   $148.75   $148.80  
  Purchase #4 $37.32   12.240%   $41.888   $41.89   $41.90   $41.90  
  Purchase #5 $213.60   13.119%   $241.6222   $241.62   $241.60   $241.60  
  Purchase #6 $227.41   10.796%   $251.9612   $251.96   $251.95   $252.00  
  Purchase #7 $64.32   4.143%   $66.9848   $66.98   $67.00   $67.00  
  7 purchase totals = $962.88       $1,064.6377   $1,064.62   $1,064.60   $1,064.70