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 $114.41   10.533%   $126.4608   $126.46   $126.45   $126.50  
  Purchase #2 $221.92   13.684%   $252.2875   $252.29   $252.30   $252.30  
  Purchase #3 $140.44   4.485%   $146.7387   $146.74   $146.75   $146.70  
  Purchase #4 $135.66   4.683%   $142.013   $142.01   $142.00   $142.00  
  Purchase #5 $219.48   7.432%   $235.7918   $235.79   $235.80   $235.80  
  Purchase #6 $62.61   10.278%   $69.0451   $69.05   $69.05   $69.00  
  Purchase #7 $79.50   11.213%   $88.4143   $88.41   $88.40   $88.40  
  7 purchase totals = $974.02       $1,060.7512   $1,060.75   $1,060.75   $1,060.70