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 $54.79   11.353%   $61.0103   $61.01   $61.00   $61.00  
  Purchase #2 $133.47   6.842%   $142.602   $142.60   $142.60   $142.60  
  Purchase #3 $165.28   6.472%   $175.9769   $175.98   $176.00   $176.00  
  Purchase #4 $147.80   5.670%   $156.1803   $156.18   $156.20   $156.20  
  Purchase #5 $159.29   3.693%   $165.1726   $165.17   $165.15   $165.20  
  Purchase #6 $223.30   5.718%   $236.0683   $236.07   $236.05   $236.10  
  Purchase #7 $193.60   10.102%   $213.1575   $213.16   $213.15   $213.20  
  7 purchase totals = $1,077.53       $1,150.1679   $1,150.17   $1,150.15   $1,150.30