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 $70.95   6.650%   $75.6682   $75.67   $75.65   $75.70  
  Purchase #2 $214.83   6.408%   $228.5963   $228.60   $228.60   $228.60  
  Purchase #3 $83.89   5.735%   $88.7011   $88.70   $88.70   $88.70  
  Purchase #4 $106.80   7.307%   $114.6039   $114.60   $114.60   $114.60  
  Purchase #5 $250.51   6.786%   $267.5096   $267.51   $267.50   $267.50  
  Purchase #6 $201.92   12.420%   $226.9985   $227.00   $227.00   $227.00  
  Purchase #7 $13.74   8.237%   $14.8718   $14.87   $14.85   $14.90  
  7 purchase totals = $942.64       $1,016.9494   $1,016.95   $1,016.90   $1,017.00