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 $23.25   11.793%   $25.9919   $25.99   $26.00   $26.00  
  Purchase #2 $248.48   12.350%   $279.1673   $279.17   $279.15   $279.20  
  Purchase #3 $243.57   6.144%   $258.5349   $258.53   $258.55   $258.50  
  Purchase #4 $65.73   3.412%   $67.9727   $67.97   $67.95   $68.00  
  Purchase #5 $224.70   13.641%   $255.3513   $255.35   $255.35   $255.40  
  Purchase #6 $94.83   5.592%   $100.1329   $100.13   $100.15   $100.10  
  Purchase #7 $61.73   6.104%   $65.498   $65.50   $65.50   $65.50  
  7 purchase totals = $962.29       $1,052.6490   $1,052.64   $1,052.65   $1,052.70