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 $241.27   8.813%   $262.5331   $262.53   $262.55   $262.50  
  Purchase #2 $135.82   8.376%   $147.1963   $147.20   $147.20   $147.20  
  Purchase #3 $222.86   10.697%   $246.6993   $246.70   $246.70   $246.70  
  Purchase #4 $175.60   12.827%   $198.1242   $198.12   $198.10   $198.10  
  Purchase #5 $181.60   8.493%   $197.0233   $197.02   $197.00   $197.00  
  Purchase #6 $23.62   6.494%   $25.1539   $25.15   $25.15   $25.20  
  Purchase #7 $189.59   8.641%   $205.9725   $205.97   $205.95   $206.00  
  7 purchase totals = $1,170.36       $1,282.7026   $1,282.69   $1,282.65   $1,282.70