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 $192.53   6.488%   $205.0213   $205.02   $205.00   $205.00  
  Purchase #2 $222.40   11.198%   $247.3044   $247.30   $247.30   $247.30  
  Purchase #3 $153.95   13.159%   $174.2083   $174.21   $174.20   $174.20  
  Purchase #4 $111.78   13.325%   $126.6747   $126.67   $126.65   $126.70  
  Purchase #5 $22.55   11.599%   $25.1656   $25.17   $25.15   $25.20  
  Purchase #6 $195.94   9.185%   $213.9371   $213.94   $213.95   $213.90  
  Purchase #7 $125.47   6.760%   $133.9518   $133.95   $133.95   $134.00  
  7 purchase totals = $1,024.62       $1,126.2632   $1,126.26   $1,126.20   $1,126.30