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 $219.65   9.837%   $241.257   $241.26   $241.25   $241.30  
  Purchase #2 $62.87   11.830%   $70.3075   $70.31   $70.30   $70.30  
  Purchase #3 $218.43   5.672%   $230.8193   $230.82   $230.80   $230.80  
  Purchase #4 $233.58   7.195%   $250.3861   $250.39   $250.40   $250.40  
  Purchase #5 $96.34   8.841%   $104.8574   $104.86   $104.85   $104.90  
  Purchase #6 $239.33   4.726%   $250.6407   $250.64   $250.65   $250.60  
  Purchase #7 $44.29   6.704%   $47.2592   $47.26   $47.25   $47.30  
  7 purchase totals = $1,114.49       $1,195.5272   $1,195.54   $1,195.50   $1,195.60