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 $52.61   9.529%   $57.6232   $57.62   $57.60   $57.60  
  Purchase #2 $58.84   8.392%   $63.7779   $63.78   $63.80   $63.80  
  Purchase #3 $215.86   11.693%   $241.1005   $241.10   $241.10   $241.10  
  Purchase #4 $211.73   12.207%   $237.5759   $237.58   $237.60   $237.60  
  Purchase #5 $98.65   12.183%   $110.6685   $110.67   $110.65   $110.70  
  Purchase #6 $77.73   9.126%   $84.8236   $84.82   $84.80   $84.80  
  Purchase #7 $209.29   6.749%   $223.415   $223.42   $223.40   $223.40  
  7 purchase totals = $924.71       $1,018.9846   $1,018.99   $1,018.95   $1,019.00