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 $180.69   8.450%   $195.9583   $195.96   $195.95   $196.00  
  Purchase #2 $249.30   11.251%   $277.3487   $277.35   $277.35   $277.30  
  Purchase #3 $107.87   9.599%   $118.2244   $118.22   $118.20   $118.20  
  Purchase #4 $106.57   8.645%   $115.783   $115.78   $115.80   $115.80  
  Purchase #5 $174.63   9.462%   $191.1535   $191.15   $191.15   $191.20  
  Purchase #6 $248.26   12.265%   $278.7091   $278.71   $278.70   $278.70  
  Purchase #7 $173.64   7.444%   $186.5658   $186.57   $186.55   $186.60  
  7 purchase totals = $1,240.96       $1,363.7428   $1,363.74   $1,363.70   $1,363.80