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 $118.45   13.723%   $134.7049   $134.70   $134.70   $134.70  
  Purchase #2 $197.29   13.545%   $224.0129   $224.01   $224.00   $224.00  
  Purchase #3 $47.95   4.484%   $50.1001   $50.10   $50.10   $50.10  
  Purchase #4 $110.61   11.440%   $123.2638   $123.26   $123.25   $123.30  
  Purchase #5 $157.33   3.156%   $162.2953   $162.30   $162.30   $162.30  
  Purchase #6 $142.88   9.631%   $156.6408   $156.64   $156.65   $156.60  
  Purchase #7 $211.70   5.504%   $223.352   $223.35   $223.35   $223.40  
  7 purchase totals = $986.21       $1,074.3698   $1,074.36   $1,074.35   $1,074.40