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 $223.52   5.428%   $235.6527   $235.65   $235.65   $235.70  
  Purchase #2 $25.99   13.104%   $29.3957   $29.40   $29.40   $29.40  
  Purchase #3 $137.49   4.299%   $143.4007   $143.40   $143.40   $143.40  
  Purchase #4 $120.44   5.134%   $126.6234   $126.62   $126.60   $126.60  
  Purchase #5 $65.90   13.478%   $74.782   $74.78   $74.80   $74.80  
  Purchase #6 $45.75   13.605%   $51.9743   $51.97   $51.95   $52.00  
  Purchase #7 $178.62   12.224%   $200.4545   $200.45   $200.45   $200.50  
  7 purchase totals = $797.71       $862.2833   $862.27   $862.25   $862.40