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 $204.68   9.403%   $223.9261   $223.93   $223.95   $223.90  
  Purchase #2 $249.87   6.319%   $265.6593   $265.66   $265.65   $265.70  
  Purchase #3 $8.46   9.391%   $9.2545   $9.25   $9.25   $9.30  
  Purchase #4 $73.80   3.158%   $76.1306   $76.13   $76.15   $76.10  
  Purchase #5 $52.94   6.612%   $56.4404   $56.44   $56.45   $56.40  
  Purchase #6 $222.62   9.599%   $243.9893   $243.99   $244.00   $244.00  
  Purchase #7 $217.96   4.783%   $228.385   $228.39   $228.40   $228.40  
  7 purchase totals = $1,030.33       $1,103.7852   $1,103.79   $1,103.85   $1,103.80