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 $210.96   3.841%   $219.063   $219.06   $219.05   $219.10  
  Purchase #2 $242.67   4.216%   $252.901   $252.90   $252.90   $252.90  
  Purchase #3 $26.36   10.104%   $29.0234   $29.02   $29.00   $29.00  
  Purchase #4 $76.98   9.505%   $84.2969   $84.30   $84.30   $84.30  
  Purchase #5 $52.49   9.399%   $57.4235   $57.42   $57.40   $57.40  
  Purchase #6 $94.80   9.782%   $104.0733   $104.07   $104.05   $104.10  
  Purchase #7 $244.57   8.318%   $264.9133   $264.91   $264.90   $264.90  
  7 purchase totals = $948.83       $1,011.6944   $1,011.68   $1,011.60   $1,011.70