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 $59.28   7.565%   $63.7645   $63.76   $63.75   $63.80  
  Purchase #2 $51.55   13.363%   $58.4386   $58.44   $58.45   $58.40  
  Purchase #3 $47.87   6.497%   $50.9801   $50.98   $51.00   $51.00  
  Purchase #4 $240.50   10.297%   $265.2643   $265.26   $265.25   $265.30  
  Purchase #5 $156.27   10.333%   $172.4174   $172.42   $172.40   $172.40  
  Purchase #6 $212.85   8.798%   $231.5765   $231.58   $231.60   $231.60  
  Purchase #7 $211.33   4.561%   $220.9688   $220.97   $220.95   $221.00  
  7 purchase totals = $979.65       $1,063.4102   $1,063.41   $1,063.40   $1,063.50