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 $57.58   4.712%   $60.2932   $60.29   $60.30   $60.30  
  Purchase #2 $248.71   7.545%   $267.4752   $267.48   $267.50   $267.50  
  Purchase #3 $91.64   4.848%   $96.0827   $96.08   $96.10   $96.10  
  Purchase #4 $164.29   10.758%   $181.9643   $181.96   $181.95   $182.00  
  Purchase #5 $17.76   5.596%   $18.7538   $18.75   $18.75   $18.80  
  Purchase #6 $198.78   7.819%   $214.3226   $214.32   $214.30   $214.30  
  Purchase #7 $243.72   11.785%   $272.4424   $272.44   $272.45   $272.40  
  7 purchase totals = $1,022.48       $1,111.3342   $1,111.32   $1,111.35   $1,111.40