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 $90.84   4.611%   $95.0286   $95.03   $95.05   $95.00  
  Purchase #2 $201.56   12.690%   $227.138   $227.14   $227.15   $227.10  
  Purchase #3 $59.48   3.590%   $61.6153   $61.62   $61.60   $61.60  
  Purchase #4 $218.44   6.562%   $232.774   $232.77   $232.75   $232.80  
  Purchase #5 $125.99   3.419%   $130.2976   $130.30   $130.30   $130.30  
  Purchase #6 $162.79   13.568%   $184.8773   $184.88   $184.90   $184.90  
  Purchase #7 $91.97   6.271%   $97.7374   $97.74   $97.75   $97.70  
  7 purchase totals = $951.07       $1,029.4682   $1,029.48   $1,029.50   $1,029.40