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 $182.64   8.366%   $197.9197   $197.92   $197.90   $197.90  
  Purchase #2 $65.43   11.758%   $73.1233   $73.12   $73.10   $73.10  
  Purchase #3 $227.65   10.594%   $251.7672   $251.77   $251.75   $251.80  
  Purchase #4 $41.78   12.836%   $47.1429   $47.14   $47.15   $47.10  
  Purchase #5 $151.72   7.182%   $162.6165   $162.62   $162.60   $162.60  
  Purchase #6 $148.26   5.573%   $156.5225   $156.52   $156.50   $156.50  
  Purchase #7 $202.37   6.206%   $214.9291   $214.93   $214.95   $214.90  
  7 purchase totals = $1,019.85       $1,104.0212   $1,104.02   $1,103.95   $1,103.90