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 $47.94   8.699%   $52.1103   $52.11   $52.10   $52.10  
  Purchase #2 $151.98   6.629%   $162.0548   $162.05   $162.05   $162.10  
  Purchase #3 $68.49   9.585%   $75.0548   $75.05   $75.05   $75.10  
  Purchase #4 $70.83   9.650%   $77.6651   $77.67   $77.65   $77.70  
  Purchase #5 $71.66   5.833%   $75.8399   $75.84   $75.85   $75.80  
  Purchase #6 $241.79   13.411%   $274.2165   $274.22   $274.20   $274.20  
  Purchase #7 $84.40   10.811%   $93.5245   $93.52   $93.50   $93.50  
  7 purchase totals = $737.09       $810.4659   $810.46   $810.40   $810.50