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 $73.65   3.119%   $75.9471   $75.95   $75.95   $75.90  
  Purchase #2 $163.76   4.465%   $171.0719   $171.07   $171.05   $171.10  
  Purchase #3 $168.94   10.108%   $186.0165   $186.02   $186.00   $186.00  
  Purchase #4 $172.44   13.466%   $195.6608   $195.66   $195.65   $195.70  
  Purchase #5 $200.80   3.498%   $207.824   $207.82   $207.80   $207.80  
  Purchase #6 $5.88   5.134%   $6.1819   $6.18   $6.20   $6.20  
  Purchase #7 $222.86   12.572%   $250.878   $250.88   $250.90   $250.90  
  7 purchase totals = $1,008.33       $1,093.5802   $1,093.58   $1,093.55   $1,093.60