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 $54.81   13.720%   $62.3299   $62.33   $62.35   $62.30  
  Purchase #2 $244.29   7.771%   $263.2738   $263.27   $263.25   $263.30  
  Purchase #3 $91.34   5.115%   $96.012   $96.01   $96.00   $96.00  
  Purchase #4 $47.92   11.212%   $53.2928   $53.29   $53.30   $53.30  
  Purchase #5 $183.60   9.558%   $201.1485   $201.15   $201.15   $201.10  
  Purchase #6 $198.42   4.502%   $207.3529   $207.35   $207.35   $207.40  
  Purchase #7 $168.57   6.320%   $179.2236   $179.22   $179.20   $179.20  
  7 purchase totals = $988.95       $1,062.6335   $1,062.62   $1,062.60   $1,062.60