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 $44.77   9.790%   $49.153   $49.15   $49.15   $49.20  
  Purchase #2 $185.80   7.460%   $199.6607   $199.66   $199.65   $199.70  
  Purchase #3 $224.68   4.211%   $234.1413   $234.14   $234.15   $234.10  
  Purchase #4 $63.45   4.477%   $66.2907   $66.29   $66.30   $66.30  
  Purchase #5 $179.62   13.611%   $204.0681   $204.07   $204.05   $204.10  
  Purchase #6 $179.52   4.481%   $187.5643   $187.56   $187.55   $187.60  
  Purchase #7 $174.96   11.829%   $195.656   $195.66   $195.65   $195.70  
  7 purchase totals = $1,052.80       $1,136.5341   $1,136.53   $1,136.50   $1,136.70