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 $23.93   11.475%   $26.676   $26.68   $26.70   $26.70  
  Purchase #2 $250.58   5.579%   $264.5599   $264.56   $264.55   $264.60  
  Purchase #3 $54.93   5.614%   $58.0138   $58.01   $58.00   $58.00  
  Purchase #4 $11.50   9.547%   $12.5979   $12.60   $12.60   $12.60  
  Purchase #5 $219.67   10.864%   $243.5349   $243.53   $243.55   $243.50  
  Purchase #6 $180.90   8.182%   $195.7012   $195.70   $195.70   $195.70  
  Purchase #7 $207.54   6.853%   $221.7627   $221.76   $221.75   $221.80  
  7 purchase totals = $949.05       $1,022.8464   $1,022.84   $1,022.85   $1,022.90