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 $33.27   6.857%   $35.5513   $35.55   $35.55   $35.60  
  Purchase #2 $84.46   8.373%   $91.5318   $91.53   $91.55   $91.50  
  Purchase #3 $166.96   5.774%   $176.6003   $176.60   $176.60   $176.60  
  Purchase #4 $174.84   10.725%   $193.5916   $193.59   $193.60   $193.60  
  Purchase #5 $211.39   11.540%   $235.7844   $235.78   $235.80   $235.80  
  Purchase #6 $213.97   8.130%   $231.3658   $231.37   $231.35   $231.40  
  Purchase #7 $137.86   3.146%   $142.1971   $142.20   $142.20   $142.20  
  7 purchase totals = $1,022.75       $1,106.6223   $1,106.62   $1,106.65   $1,106.70