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 $208.80   5.771%   $220.8498   $220.85   $220.85   $220.80  
  Purchase #2 $196.74   7.118%   $210.744   $210.74   $210.75   $210.70  
  Purchase #3 $68.79   3.187%   $70.9823   $70.98   $71.00   $71.00  
  Purchase #4 $77.29   3.337%   $79.8692   $79.87   $79.85   $79.90  
  Purchase #5 $87.41   9.858%   $96.0269   $96.03   $96.05   $96.00  
  Purchase #6 $238.87   11.760%   $266.9611   $266.96   $266.95   $267.00  
  Purchase #7 $225.85   11.122%   $250.969   $250.97   $250.95   $251.00  
  7 purchase totals = $1,103.75       $1,196.4023   $1,196.40   $1,196.40   $1,196.40